Mathematics with Applications In the Management, Natural, and Social Sciences (12th Edition)
12th Edition
ISBN: 9780134767628
Author: Margaret L. Lial, Thomas W. Hungerford, John P. Holcomb, Bernadette Mullins
Publisher: PEARSON
expand_more
expand_more
format_list_bulleted
Videos
Question
Chapter 6.4, Problem 12E
To determine
To Calculate: The sum of two matrices
Expert Solution & Answer
Want to see the full answer?
Check out a sample textbook solution
Students have asked these similar questions
Melissa claims the triangles are similar. Is her claim correct? If her claim is correct, state the transformations that map
△MNO
△MNO
onto
△PRQ.
△PRQ.
If her claim is not correct, explain why.
2 (VaR and ES) Suppose X1
are independent. Prove that
~
Unif[-0.5, 0.5] and X2
VaRa (X1X2) < VaRa(X1) + VaRa (X2).
~
Unif[-0.5, 0.5]
8 (Correlation and Diversification)
Assume we have two stocks, A and B, show that a particular combination
of the two stocks produce a risk-free portfolio when the correlation between
the return of A and B is -1.
Chapter 6 Solutions
Mathematics with Applications In the Management, Natural, and Social Sciences (12th Edition)
Ch. 6.1 - Checkpoint1 Use the substitution method tosolve...Ch. 6.1 - Checkpoint 2
Use the elimination method to solve...Ch. 6.1 - Checkpoint 3
Solve the system of equations .
Draw...Ch. 6.1 - Checkpoint 4
Solve the following system:
Ch. 6.1 - Checkpoint 5
Solve the system
Draw the graph of...Ch. 6.1 - Prob. 6CPCh. 6.1 - Prob. 1ECh. 6.1 - Prob. 2ECh. 6.1 - Use substitution to solve each system. (See...Ch. 6.1 - Use substitution to solve each system. (See...
Ch. 6.1 - Use substitution to solve each system. (See...Ch. 6.1 - Use substitution to solve each system. (See...Ch. 6.1 - Use elimination to solve each system. (See...Ch. 6.1 - Use elimination to solve each system. (See...Ch. 6.1 - Use elimination to solve each system. (See...Ch. 6.1 - Use elimination to solve each system. (See...Ch. 6.1 - Use elimination to solve each system. (See...Ch. 6.1 - Prob. 12ECh. 6.1 - Prob. 13ECh. 6.1 - Use elimination to solve each system. (See...Ch. 6.1 - Use elimination to solve each system. (See...Ch. 6.1 - Prob. 16ECh. 6.1 - In Exercises 17 and 18, multiply both sides of...Ch. 6.1 - In Exercises 17 and 18, multiply both sides of...Ch. 6.1 - Millennials The number of baby boomers has been...Ch. 6.1 - Prob. 20ECh. 6.1 - Slow Midwestern Growth According to US. Census...Ch. 6.1 - Booming Florida At the start of the millennium,...Ch. 6.1 - Google Trends According to Google Trends, popular...Ch. 6.1 -
24. Heart Disease and Cancer Deaths The number of...Ch. 6.1 - Workforce Participation for Women and Men On the...Ch. 6.1 - Prob. 26ECh. 6.1 - Theater Tickets A 200-seat theater charges $8 for...Ch. 6.1 - Prob. 28ECh. 6.1 - Prob. 29ECh. 6.1 - Prob. 30ECh. 6.1 - Prob. 31ECh. 6.1 - Prob. 32ECh. 6.2 - Checkpoint 1
Use the elimination method to solve...Ch. 6.2 - Prob. 2CPCh. 6.2 - Checkpoint 3 Perform the given row operations on...Ch. 6.2 - Prob. 4CPCh. 6.2 - Prob. 5CPCh. 6.2 - Prob. 6CPCh. 6.2 - Prob. 7CPCh. 6.2 - Checkpoint 8
Solve each system.
(a)
(b)
Ch. 6.2 - Prob. 9CPCh. 6.2 - Prob. 1ECh. 6.2 - Prob. 2ECh. 6.2 - Prob. 3ECh. 6.2 - Prob. 4ECh. 6.2 - Prob. 5ECh. 6.2 - Prob. 6ECh. 6.2 - Obtain an equivalent system by performing the...Ch. 6.2 - Obtain an equivalent system by performing the...Ch. 6.2 - Obtain an equivalent system by performing the...Ch. 6.2 - Prob. 10ECh. 6.2 - Prob. 11ECh. 6.2 - Obtain an equivalent system by performing the...Ch. 6.2 - Prob. 13ECh. 6.2 - Write the augmented matrix of each of the given...Ch. 6.2 - Prob. 15ECh. 6.2 - Prob. 16ECh. 6.2 - Prob. 17ECh. 6.2 - Prob. 18ECh. 6.2 - Prob. 22ECh. 6.2 - Prob. 21ECh. 6.2 - Use the indicated row operation to transform each...Ch. 6.2 - Prob. 20ECh. 6.2 - In Exercises 21-24, the reduced row echelon form...Ch. 6.2 - In Exercises 21-24, the reduced row echelon form...Ch. 6.2 - In Exercises 21-24, the reduced row echelon form...Ch. 6.2 - In Exercises 21-24, the reduced row echelon form...Ch. 6.2 - Prob. 25ECh. 6.2 - Prob. 28ECh. 6.2 - In Exercises 25-30, perform row operations on the...Ch. 6.2 - In Exercises 25-30, perform row operations on the...Ch. 6.2 - In Exercises 25-30, perform row operations on the...Ch. 6.2 - Prob. 32ECh. 6.2 - Prob. 33ECh. 6.2 - Prob. 34ECh. 6.2 - Write the augmented matrix of the system and use...Ch. 6.2 - Write the augmented matrix of the system and use...Ch. 6.2 - Write the augmented matrix of the system and use...Ch. 6.2 - Write the augmented matrix of the system and use...Ch. 6.2 - Write the augmented matrix of the system and use...Ch. 6.2 - Prob. 40ECh. 6.2 - Prob. 41ECh. 6.2 - Write the augmented matrix of the system and use...Ch. 6.2 - Use the Gauss-Jordan method to solve each of the...Ch. 6.2 - Prob. 44ECh. 6.2 - Prob. 45ECh. 6.2 - Prob. 46ECh. 6.2 - Prob. 47ECh. 6.2 - Prob. 48ECh. 6.2 - Prob. 49ECh. 6.2 - Prob. 55ECh. 6.2 - Prob. 50ECh. 6.2 - Prob. 51ECh. 6.2 - Prob. 52ECh. 6.2 - Prob. 53ECh. 6.2 - Prob. 54ECh. 6.2 - Prob. 56ECh. 6.2 - Prob. 57ECh. 6.2 - Prob. 58ECh. 6.2 - Prob. 59ECh. 6.2 - Prob. 60ECh. 6.2 - Prob. 61ECh. 6.2 - Prob. 62ECh. 6.2 - Solve the system by any method.
62.
Ch. 6.2 - Prob. 63ECh. 6.2 - Prob. 65ECh. 6.2 - Prob. 66ECh. 6.2 - Prob. 67ECh. 6.2 - Prob. 68ECh. 6.2 - Prob. 69ECh. 6.2 - Prob. 70ECh. 6.2 - Prob. 71ECh. 6.2 - 72. Explain why a system with more variables than...Ch. 6.3 - Checkpoint 1 In Example 1, suppose that the...Ch. 6.3 - Checkpoint 2 Write the augmented matrix of the...Ch. 6.3 - Prob. 3CPCh. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Prob. 3ECh. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Prob. 7ECh. 6.3 - Prob. 8ECh. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Prob. 10ECh. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Prob. 12ECh. 6.3 - Prob. 13ECh. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Prob. 16ECh. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - Use systems of equations to work these applied...Ch. 6.3 - A graphing calculator or other technology is...Ch. 6.3 - A graphing calculator or other technology is...Ch. 6.3 - 25. Social Science The table shows Census Bureau...Ch. 6.3 - 26. Social Science The table shows Census Bureau...Ch. 6.3 - 27. Business At a pottery factory, fuel...Ch. 6.3 - Prob. 28ECh. 6.4 - Checkpoint 1
Rewrite matrix M in Example 1 in a...Ch. 6.4 - Prob. 2CPCh. 6.4 - Prob. 3CPCh. 6.4 - Prob. 4CPCh. 6.4 - Prob. 5CPCh. 6.4 - Prob. 6CPCh. 6.4 - Prob. 7CPCh. 6.4 - Prob. 8CPCh. 6.4 - Prob. 9CPCh. 6.4 - Prob. 1ECh. 6.4 - Prob. 2ECh. 6.4 - Prob. 3ECh. 6.4 - Prob. 4ECh. 6.4 - Prob. 5ECh. 6.4 - Prob. 6ECh. 6.4 - Prob. 7ECh. 6.4 - Find the size of each of the given matrices....Ch. 6.4 - Prob. 9ECh. 6.4 - Prob. 10ECh. 6.4 - Prob. 11ECh. 6.4 - Perform the indicated operations where possible....Ch. 6.4 - Prob. 14ECh. 6.4 - Perform the indicated operations where possible....Ch. 6.4 - Prob. 15ECh. 6.4 - Prob. 16ECh. 6.4 - Prob. 17ECh. 6.4 - Let and . Find each of the following. (See...Ch. 6.4 - Prob. 19ECh. 6.4 - Let and . Find each of the following. (See...Ch. 6.4 - Prob. 21ECh. 6.4 - Let and . Find each of the following. (See...Ch. 6.4 - Prob. 23ECh. 6.4 - Prob. 24ECh. 6.4 - Prob. 25ECh. 6.4 - Prob. 26ECh. 6.4 - Prob. 27ECh. 6.4 - Using matrices
verify that the statements in...Ch. 6.4 - Prob. 29ECh. 6.4 - Prob. 30ECh. 6.4 - Work the following exercises. (See Example...Ch. 6.4 - Prob. 32ECh. 6.4 - Prob. 33ECh. 6.4 - Prob. 34ECh. 6.4 - Prob. 35ECh. 6.4 - Prob. 36ECh. 6.5 - Prob. 1CPCh. 6.5 - Prob. 2CPCh. 6.5 - Prob. 3CPCh. 6.5 - Prob. 4CPCh. 6.5 - Prob. 5CPCh. 6.5 - Prob. 6CPCh. 6.5 - Prob. 7CPCh. 6.5 - Prob. 8CPCh. 6.5 - Prob. 9CPCh. 6.5 - Prob. 1ECh. 6.5 - Prob. 2ECh. 6.5 - In Exercises 1-6, the sizes of two matrices A and...Ch. 6.5 - In Exercises 1-6, the sizes of two matrices A and...Ch. 6.5 - Prob. 5ECh. 6.5 - Prob. 6ECh. 6.5 - Prob. 7ECh. 6.5 - Prob. 8ECh. 6.5 - Prob. 9ECh. 6.5 - Prob. 10ECh. 6.5 - Find each of the following matrix products, if...Ch. 6.5 - Prob. 12ECh. 6.5 - Prob. 13ECh. 6.5 - Find each of the following matrix products, if...Ch. 6.5 - Prob. 15ECh. 6.5 - Prob. 16ECh. 6.5 - Prob. 17ECh. 6.5 - Find each of the following matrix products, if...Ch. 6.5 - Prob. 19ECh. 6.5 - Prob. 20ECh. 6.5 - Prob. 21ECh. 6.5 - Prob. 22ECh. 6.5 - Prob. 23ECh. 6.5 - Given matrices
verify that the statements in...Ch. 6.5 - Prob. 25ECh. 6.5 - Prob. 26ECh. 6.5 - Prob. 27ECh. 6.5 - Prob. 28ECh. 6.5 - Prob. 29ECh. 6.5 - Prob. 30ECh. 6.5 - Prob. 31ECh. 6.5 - Determine whether the given matrices are inverses...Ch. 6.5 - Prob. 37ECh. 6.5 - Prob. 34ECh. 6.5 - Prob. 35ECh. 6.5 - Find the inverse, if it exists, for each of the...Ch. 6.5 - Prob. 33ECh. 6.5 - Find the inverse, if it exists, for each of the...Ch. 6.5 - Prob. 39ECh. 6.5 - Prob. 40ECh. 6.5 - Find the inverse, if it exists, for each of the...Ch. 6.5 - Find the inverse, if it exists, for each of the...Ch. 6.5 - Prob. 43ECh. 6.5 - Prob. 44ECh. 6.5 - Prob. 45ECh. 6.5 - Prob. 46ECh. 6.5 - Prob. 47ECh. 6.5 - Prob. 48ECh. 6.5 - Prob. 49ECh. 6.5 - Work these exercises. (See Example 4.)
50. Bulk...Ch. 6.5 - Prob. 56ECh. 6.5 - A graphing calculator or other technology is...Ch. 6.5 - Prob. 55ECh. 6.5 - Prob. 52ECh. 6.5 - Prob. 53ECh. 6.5 - Prob. 54ECh. 6.6 - Prob. 1CPCh. 6.6 - Prob. 2CPCh. 6.6 - Prob. 3CPCh. 6.6 - Prob. 4CPCh. 6.6 - Prob. 5CPCh. 6.6 - Prob. 6CPCh. 6.6 - Prob. 7CPCh. 6.6 - Checkpoint 8
Use the following matrix to find the ...Ch. 6.6 - Prob. 9CPCh. 6.6 - Prob. 1ECh. 6.6 - Prob. 2ECh. 6.6 - Prob. 3ECh. 6.6 - Prob. 4ECh. 6.6 - Prob. 5ECh. 6.6 - Prob. 6ECh. 6.6 - Prob. 7ECh. 6.6 - Use the inverse of the coefficient matrix to solve...Ch. 6.6 - Prob. 9ECh. 6.6 - Prob. 10ECh. 6.6 - Prob. 11ECh. 6.6 - Use the inverse of the coefficient matrix to solve...Ch. 6.6 - Prob. 13ECh. 6.6 - Prob. 14ECh. 6.6 - Prob. 15ECh. 6.6 - Prob. 16ECh. 6.6 - Write a system of equations, and use the inverse...Ch. 6.6 - Prob. 18ECh. 6.6 - Prob. 20ECh. 6.6 - Prob. 19ECh. 6.6 - Write a system of equations, and use the inverse...Ch. 6.6 - 22. Health A 100-bed nursing home provides two...Ch. 6.6 - Find the production matrix for the given...Ch. 6.6 - Prob. 24ECh. 6.6 - Prob. 25ECh. 6.6 - Exercises 25 and 26 refer to Example 6.
Example 6...Ch. 6.6 - Work these problems. (See Examples 3-6.)
28....Ch. 6.6 - Prob. 27ECh. 6.6 - Prob. 29ECh. 6.6 - Work these problems. (See Examples...Ch. 6.6 - Prob. 31ECh. 6.6 - Prob. 32ECh. 6.6 - Prob. 33ECh. 6.6 - Prob. 34ECh. 6.6 - Prob. 35ECh. 6.6 - Prob. 36ECh. 6.6 - Work these coding exercises. (See Example 7 and...Ch. 6.6 - Prob. 38ECh. 6.6 - Prob. 39ECh. 6.6 - Prob. 40ECh. 6.6 - Prob. 41ECh. 6.6 - Prob. 42ECh. 6.6 - Prob. 43ECh. 6.6 - 44. Business The figure shows four southern cities...Ch. 6 - Prob. 1RECh. 6 - Solve each of the following systems.
2.
Ch. 6 - Solve each of the following systems.
3.
Ch. 6 - Solve each of the following systems.
4.
Ch. 6 - 5. Business Abigail Henderson plans to buy shares...Ch. 6 - Prob. 6RECh. 6 - Prob. 7RECh. 6 - Prob. 8RECh. 6 - Prob. 9RECh. 6 - Prob. 10RECh. 6 - Prob. 11RECh. 6 - Prob. 12RECh. 6 - Prob. 13RECh. 6 - Prob. 14RECh. 6 - Prob. 15RECh. 6 - Prob. 16RECh. 6 - Prob. 17RECh. 6 - Prob. 18RECh. 6 - Prob. 19RECh. 6 - Prob. 20RECh. 6 - Prob. 21RECh. 6 - Prob. 22RECh. 6 - Prob. 23RECh. 6 - Prob. 24RECh. 6 - Prob. 25RECh. 6 - Prob. 26RECh. 6 - Prob. 27RECh. 6 - Prob. 28RECh. 6 - Prob. 29RECh. 6 - Prob. 30RECh. 6 - Prob. 31RECh. 6 - Prob. 32RECh. 6 - Prob. 33RECh. 6 - Prob. 34RECh. 6 - Prob. 35RECh. 6 - Prob. 36RECh. 6 - Prob. 37RECh. 6 - Prob. 38RECh. 6 - Prob. 39RECh. 6 - Prob. 40RECh. 6 - Prob. 41RECh. 6 - Prob. 42RECh. 6 - Prob. 43RECh. 6 - Prob. 44RECh. 6 - Prob. 45RECh. 6 - Prob. 46RECh. 6 - Prob. 47RECh. 6 - Prob. 48RECh. 6 - Prob. 49RECh. 6 - Prob. 50RECh. 6 - Prob. 51RECh. 6 - Prob. 52RECh. 6 - Prob. 53RECh. 6 - Prob. 54RECh. 6 - Prob. 55RECh. 6 - Prob. 56RECh. 6 - Prob. 57RECh. 6 - Prob. 58RECh. 6 - Prob. 59RECh. 6 - Prob. 60RECh. 6 - Prob. 61RECh. 6 - Prob. 62RECh. 6 - Prob. 63RECh. 6 - Prob. 64RECh. 6 - Prob. 65RECh. 6 - Prob. 66RECh. 6 - Prob. 67RECh. 6 - Prob. 68RECh. 6 - Prob. 69RECh. 6 - Prob. 70RECh. 6 - Prob. 71RECh. 6 - Prob. 72RECh. 6 - Prob. 73RECh. 6 - Prob. 74RECh. 6 - Prob. 75RECh. 6 - Prob. 76RECh. 6 - Prob. 77RECh. 6 - Prob. 78RECh. 6 - Prob. 79RECh. 6 - Prob. 80RECh. 6 - Prob. 81RECh. 6 - Prob. 82RECh. 6 - Prob. 83RECh. 6 - Prob. 84RECh. 6 - Prob. 85RECh. 6 - Solve each of the following problems by any...Ch. 6 - Prob. 87RECh. 6 - Prob. 88RECh. 6 - Prob. 89RECh. 6 - Use technology to do Exercises 89-91.
90. Business...Ch. 6 - Prob. 91RECh. 6 - Prob. 92RECh. 6 - Prob. 93RECh. 6 - Prob. 94RECh. 6 - Prob. 95RECh. 6 - Prob. 96RECh. 6 - Prob. 1CECh. 6 - 2. It was shown previously that there are four...Ch. 6 - 3. Which trips in the Stampede Air network take...Ch. 6 - Prob. 4CECh. 6 - Prob. 5CECh. 6 - Prob. 6CE
Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, subject and related others by exploring similar questions and additional content below.Similar questions
- 9 (Portfolio allocation) Suppose R₁ and R2 are returns of 2 assets and with expected return and variance respectively r₁ and 72 and variance-covariance σ2, 0%½ and σ12. Find −∞ ≤ w ≤ ∞ such that the portfolio wR₁ + (1 - w) R₂ has the smallest risk.arrow_forward7 (Multivariate random variable) Suppose X, €1, €2, €3 are IID N(0, 1) and Y2 Y₁ = 0.2 0.8X + €1, Y₂ = 0.3 +0.7X+ €2, Y3 = 0.2 + 0.9X + €3. = (In models like this, X is called the common factors of Y₁, Y₂, Y3.) Y = (Y1, Y2, Y3). (a) Find E(Y) and cov(Y). (b) What can you observe from cov(Y). Writearrow_forward1 (VaR and ES) Suppose X ~ f(x) with 1+x, if 0> x > −1 f(x) = 1−x if 1 x > 0 Find VaRo.05 (X) and ES0.05 (X).arrow_forward
- (^) k Recall that for numbers 0 ≤ k ≤ n the binomial coefficient (^) is defined as n! k! (n−k)! Question 1. (1) Prove the following identity: (22) + (1121) = (n+1). (2) Use the identity above to prove the binomial theorem by induction. That is, prove that for any a, b = R, n (a + b)" = Σ (^) an- n-kyk. k=0 n Recall that Σ0 x is short hand notation for the expression x0+x1+ +xn- (3) Fix x = R, x > 0. Prove Bernoulli's inequality: (1+x)" ≥1+nx, by using the binomial theorem. - Question 2. Prove that ||x| - |y|| ≤ |x − y| for any real numbers x, y. Question 3. Assume (In) nEN is a sequence which is unbounded above. That is, the set {xn|nЄN} is unbounded above. Prove that there are natural numbers N] k for all k Є N. be natural numbers (nk Є N). Prove thatarrow_forwardQuestion content area top Part 1 Find the measure of ABC for the congruent triangles ABC and Upper A prime Upper B prime Upper C primeA′B′C′. 79 degrees79° 1533 2930 Part 1 m ABCequals=enter your response heredegreesarrow_forwardJoy is making Christmas gifts. She has 6 1/12 feet of yarn and will need 4 1/4 to complete our project. How much yarn will she have left over compute this solution in two different ways arrow_forward
- Solve for X. Explain each step. 2^2x • 2^-4=8arrow_forwardFind the range and all the answers. Remark that the range isn’t between -(pi/2) and (pi/2)arrow_forwardOne hundred people were surveyed, and one question pertained to their educational background. The results of this question and their genders are given in the following table. Female (F) Male (F′) Total College degree (D) 30 20 50 No college degree (D′) 30 20 50 Total 60 40 100 If a person is selected at random from those surveyed, find the probability of each of the following events.1. The person is female or has a college degree. Answer: equation editor Equation Editor 2. The person is male or does not have a college degree. Answer: equation editor Equation Editor 3. The person is female or does not have a college degree.arrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
Discrete Mathematics and Its Applications ( 8th I...MathISBN:9781259676512Author:Kenneth H RosenPublisher:McGraw-Hill Education
Mathematics for Elementary Teachers with Activiti...MathISBN:9780134392790Author:Beckmann, SybillaPublisher:PEARSON
Thinking Mathematically (7th Edition)MathISBN:9780134683713Author:Robert F. BlitzerPublisher:PEARSON
Discrete Mathematics With ApplicationsMathISBN:9781337694193Author:EPP, Susanna S.Publisher:Cengage Learning,
Pathways To Math Literacy (looseleaf)MathISBN:9781259985607Author:David Sobecki Professor, Brian A. MercerPublisher:McGraw-Hill Education
Discrete Mathematics and Its Applications ( 8th I...
Math
ISBN:9781259676512
Author:Kenneth H Rosen
Publisher:McGraw-Hill Education
Mathematics for Elementary Teachers with Activiti...
Math
ISBN:9780134392790
Author:Beckmann, Sybilla
Publisher:PEARSON
Thinking Mathematically (7th Edition)
Math
ISBN:9780134683713
Author:Robert F. Blitzer
Publisher:PEARSON
Discrete Mathematics With Applications
Math
ISBN:9781337694193
Author:EPP, Susanna S.
Publisher:Cengage Learning,
Pathways To Math Literacy (looseleaf)
Math
ISBN:9781259985607
Author:David Sobecki Professor, Brian A. Mercer
Publisher:McGraw-Hill Education
Introduction to Integers,Maths - What are integers - English; Author: Mathispower4u;https://www.youtube.com/watch?v=04pURxo-iu0;License: Standard YouTube License, CC-BY
Integers-Middle School Math; Author: MooMooMath and Science;https://www.youtube.com/watch?v=DGWcWtqM_yk;License: Standard YouTube License, CC-BY