BEGINNING+INTERM.ALG.(LL) >CUSTOM PKG.<
BEGINNING+INTERM.ALG.(LL) >CUSTOM PKG.<
6th Edition
ISBN: 9781266148941
Author: Miller
Publisher: MCG CUSTOM
bartleby

Videos

Question
Book Icon
Chapter 4.5, Problem 31PE
To determine

If the given system of equations is dependent or inconsistent or has a unique solution. If there is a unique solution, solve for it. The system of equations is given as follows:

2x+y+3z=2x−y+2z=−4−2x+2y−4z=8

Expert Solution & Answer
Check Mark

Want to see the full answer?

Check out a sample textbook solution
Blurred answer
Previous
Chapter 4.5, Problem 30PE
Next
Chapter 4.5, Problem 32PE
Students have asked these similar questions
An important application of systems of equations arises in connection with supply and demand. As the price of a product increases, the demand for that product decreases. However, at higher prices, suppliers are willing to produce greater quantities of the product. Exercises 97–98 involve supply and demand. 97. A chain of electronics stores sells hand-held color televisions. The weekly demand and supply models are given as follows: Number sold Demand model per week N = -5p + 750 Price of television Number supplied to the chain per week N = 2.5p. 1apow hjddns a. How many hand-held color televisions can be sold and supplied at $120 per television? b. Find the price at which supply and demand are equal. At this price, how many televisions can be supplied and sold each week?
For Exercises 15–22, solve the system by using the addition method. (See Examples 3-4) 15. 2x + 3y = 11 16. 3x + y² = 21 17. x - xy = 20 18. 4xy + 3y² = -9 2 + 4y = 8 4x - 2y = -2 -2x2 + 3xy = -44 2xy + y = -5 21. x = 1- y 9x - 4y? = 36 19. 5x - 2y2 = 1 20. 6x + 5y = 38 7x - 3y = 9 22. 4x = 4 - y? 16y = 144 + 9x? 2x - 3y = -4
Please do #6 and #20

Chapter 4 Solutions

BEGINNING+INTERM.ALG.(LL) >CUSTOM PKG.<

Ch. 4.1 - Determine whether the ordered paired is a solution...Ch. 4.1 - Determine whether the ordered paired is a solution...Ch. 4.1 - Solve the system by the graphing method. y = − 3 x...Ch. 4.1 - Solve the system by the graphing method. y = 2 x −...Ch. 4.1 - Solve the system by the graphing. 5. Ch. 4.1 - Solve the system by the graphing. 6. Ch. 4.1 - a. A______ of linear equations consists of two or...Ch. 4.1 - For Exercises 2-10, determine if the given point...Ch. 4.1 - Prob. 3PECh. 4.1 - Prob. 4PE
Ch. 4.1 - For Exercises 2-10, determine if the given point...Ch. 4.1 - Prob. 6PECh. 4.1 - Prob. 7PECh. 4.1 - Prob. 8PECh. 4.1 - Prob. 9PECh. 4.1 - Prob. 10PECh. 4.1 - For Exercises 11-14, match the graph of the system...Ch. 4.1 - Prob. 12PECh. 4.1 - Prob. 13PECh. 4.1 - For Exercises 11-14, match the graph of the system...Ch. 4.1 - Prob. 15PECh. 4.1 - Prob. 16PECh. 4.1 - Prob. 17PECh. 4.1 - Prob. 18PECh. 4.1 - Prob. 19PECh. 4.1 - Prob. 20PECh. 4.1 - For Exercises 16-26, determine which system of...Ch. 4.1 - Prob. 22PECh. 4.1 - Prob. 23PECh. 4.1 - Prob. 24PECh. 4.1 - Prob. 25PECh. 4.1 - Prob. 26PECh. 4.1 - Prob. 27PECh. 4.1 - Prob. 28PECh. 4.1 - For Exercises 27-50, solve the system by graphing....Ch. 4.1 - Prob. 30PECh. 4.1 - Prob. 31PECh. 4.1 - Prob. 32PECh. 4.1 - Prob. 33PECh. 4.1 - Prob. 34PECh. 4.1 - Prob. 35PECh. 4.1 - Prob. 36PECh. 4.1 - Prob. 37PECh. 4.1 - Prob. 38PECh. 4.1 - Prob. 39PECh. 4.1 - Prob. 40PECh. 4.1 - Prob. 41PECh. 4.1 - Prob. 42PECh. 4.1 - Prob. 43PECh. 4.1 - Prob. 44PECh. 4.1 - Prob. 45PECh. 4.1 - Prob. 46PECh. 4.1 - Prob. 47PECh. 4.1 - Prob. 48PECh. 4.1 - Prob. 49PECh. 4.1 - Prob. 50PECh. 4.1 - Prob. 51PECh. 4.1 - The cost to rent a 10 ft by 10 ft storage space is...Ch. 4.1 - For the systems graphed in Exercises 53-54,...Ch. 4.1 - For the systems graphed in Exercises 53-54,...Ch. 4.1 - Prob. 55PECh. 4.1 - Prob. 56PECh. 4.1 - Prob. 57PECh. 4.1 - Prob. 58PECh. 4.1 - Prob. 59PECh. 4.1 - Prob. 60PECh. 4.1 - Prob. 61PECh. 4.1 - Prob. 62PECh. 4.1 - One equation in a system of linear equations is x...Ch. 4.1 - Prob. 64PECh. 4.2 - Solve the system by using the substitution method....Ch. 4.2 - Prob. 2SPCh. 4.2 - Prob. 3SPCh. 4.2 - Prob. 4SPCh. 4.2 - Prob. 5SPCh. 4.2 - One number is 16 more than another. Their sum is...Ch. 4.2 - Prob. 7SPCh. 4.2 - Prob. 1PECh. 4.2 - Prob. 2PECh. 4.2 - Prob. 3PECh. 4.2 - Prob. 4PECh. 4.2 - Given the system: 4 x − 2 y = − 6 3 x +         y...Ch. 4.2 - Prob. 6PECh. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - Prob. 8PECh. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - Prob. 10PECh. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - Prob. 12PECh. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - Prob. 14PECh. 4.2 - Prob. 15PECh. 4.2 - Prob. 16PECh. 4.2 - Prob. 17PECh. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - Prob. 19PECh. 4.2 - Prob. 20PECh. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - Prob. 22PECh. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - Prob. 25PECh. 4.2 - Prob. 26PECh. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - Prob. 29PECh. 4.2 - Prob. 30PECh. 4.2 - Prob. 31PECh. 4.2 - Prob. 32PECh. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - Prob. 36PECh. 4.2 - Prob. 37PECh. 4.2 - Prob. 38PECh. 4.2 - Prob. 39PECh. 4.2 - Prob. 40PECh. 4.2 - Prob. 41PECh. 4.2 - For Exercises 13-48, solve the system by using the...Ch. 4.2 - Prob. 43PECh. 4.2 - For Exercises 49-58, set up a system of linear...Ch. 4.2 - For Exercises 49-58, set up a system of linear...Ch. 4.2 - For Exercises 49-58, set up a system of linear...Ch. 4.2 - For Exercises 49-58, set up a system of linear...Ch. 4.2 - For Exercises 49-58, set up a system of linear...Ch. 4.2 - For Exercises 49-58, set up a system of linear...Ch. 4.2 - For Exercises 49-58, set up a system of linear...Ch. 4.2 - Prob. 51PECh. 4.2 - Prob. 52PECh. 4.2 - Prob. 53PECh. 4.2 - Prob. 54PECh. 4.3 - Solve the system by using the addition method. x +...Ch. 4.3 - Solve the system by using the addition method. 4 x...Ch. 4.3 - Prob. 3SPCh. 4.3 - Solve the system by using the addition method. 15...Ch. 4.3 - Solve the system by using the addition method. 2 3...Ch. 4.3 - Solve the system by using the addition method. 3 x...Ch. 4.3 - Prob. 1PECh. 4.3 - Prob. 2PECh. 4.3 - Prob. 3PECh. 4.3 - Prob. 4PECh. 4.3 - Prob. 5PECh. 4.3 - For Exercises 6-7, answer as true or false. Given...Ch. 4.3 - Prob. 7PECh. 4.3 - Given the system 3 x − 4 y = 2 17 x + y = 35 a....Ch. 4.3 - 9. Given the system a. Which variable, x or y, is...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - Prob. 22PECh. 4.3 - Prob. 23PECh. 4.3 - For Exercises 10-24, solve each system using the...Ch. 4.3 - Prob. 25PECh. 4.3 - Prob. 26PECh. 4.3 - Prob. 27PECh. 4.3 - Prob. 28PECh. 4.3 - Prob. 29PECh. 4.3 - 30. Suppose in solving a system of linear...Ch. 4.3 - For Exercises 31-42, solve the system by using the...Ch. 4.3 - Prob. 32PECh. 4.3 - Prob. 33PECh. 4.3 - Prob. 34PECh. 4.3 - Prob. 35PECh. 4.3 - Prob. 36PECh. 4.3 - Prob. 37PECh. 4.3 - Prob. 38PECh. 4.3 - Prob. 39PECh. 4.3 - Prob. 40PECh. 4.3 - Prob. 41PECh. 4.3 - Prob. 42PECh. 4.3 - Prob. 43PECh. 4.3 - Prob. 44PECh. 4.3 - Prob. 45PECh. 4.3 - Prob. 46PECh. 4.3 - Prob. 47PECh. 4.3 - Prob. 48PECh. 4.3 - Prob. 49PECh. 4.3 - Prob. 50PECh. 4.3 - Prob. 51PECh. 4.3 - Prob. 52PECh. 4.3 - Prob. 53PECh. 4.3 - Prob. 54PECh. 4.3 - Prob. 55PECh. 4.3 - Prob. 56PECh. 4.3 - For Exercises 43-63, solve each system of...Ch. 4.3 - Prob. 58PECh. 4.3 - Prob. 59PECh. 4.3 - Prob. 60PECh. 4.3 - Prob. 61PECh. 4.3 - Prob. 62PECh. 4.3 - Prob. 63PECh. 4.3 - Prob. 64PECh. 4.3 - Prob. 65PECh. 4.3 - Prob. 66PECh. 4.3 - Prob. 67PECh. 4.3 - Prob. 68PECh. 4.3 - Prob. 69PECh. 4.3 - For Exercises 70-72, solve the system by using...Ch. 4.3 - For Exercises 70-72, solve the system by using...Ch. 4.3 - For Exercises 70-72, solve the system by using...Ch. 4.3 - 73. Explain why a system of linear equations...Ch. 4.3 - Prob. 74PECh. 4.3 - Prob. 75PECh. 4.3 - For Exercises 1–6 determine the number of...Ch. 4.3 - For Exercises 1–6 determine the number of...Ch. 4.3 - Prob. 3PRECh. 4.3 - Prob. 4PRECh. 4.3 - Prob. 5PRECh. 4.3 - For Exercises 1–6 determine the number of...Ch. 4.3 - For Exercises 7–10, a method of solving has been...Ch. 4.3 - For Exercises 7–10, a method of solving has been...Ch. 4.3 - Prob. 9PRECh. 4.3 - Prob. 10PRECh. 4.3 - For Exercises 11–30, solve each system using the...Ch. 4.3 - For Exercises 11–30, solve each system using the...Ch. 4.3 - Prob. 13PRECh. 4.3 - For Exercises 11–30, solve each system using the...Ch. 4.3 - For Exercises 11–30, solve each system using the...Ch. 4.3 - For Exercises 11–30, solve each system using the...Ch. 4.3 - For Exercises 11–30, solve each system using the...Ch. 4.3 - For Exercises 11–30, solve each system using the...Ch. 4.3 - For Exercises 11–30, solve each system using the...Ch. 4.3 - For Exercises 11–30, solve each system using the...Ch. 4.3 - For Exercises 11–30, solve each system using the...Ch. 4.3 - For Exercises 11–30, solve each system using the...Ch. 4.3 - Prob. 23PRECh. 4.3 - Prob. 24PRECh. 4.3 - Prob. 25PRECh. 4.3 - Prob. 26PRECh. 4.3 - Prob. 27PRECh. 4.3 - Prob. 28PRECh. 4.3 - Prob. 29PRECh. 4.3 - Prob. 30PRECh. 4.4 - 1. Lynn went to a fast-food restaurant and spent...Ch. 4.4 - Prob. 2SPCh. 4.4 - Prob. 3SPCh. 4.4 - Prob. 4SPCh. 4.4 - Prob. 1PECh. 4.4 - Prob. 2PECh. 4.4 - Prob. 3PECh. 4.4 - Prob. 4PECh. 4.4 - Prob. 5PECh. 4.4 - Foe Exercises 5-8, set up a system of linear...Ch. 4.4 - Prob. 7PECh. 4.4 - Prob. 8PECh. 4.4 - 9. An online store sells old video games and DVDs...Ch. 4.4 - Tanya bought three adult tickets and one...Ch. 4.4 - 11. Nora bought 100 shares of a technology stock...Ch. 4.4 - 12. Eight students in Ms. Reese’s class decided to...Ch. 4.4 - Prob. 13PECh. 4.4 - Zoey purchased some beef and some chicken for a...Ch. 4.4 - 15. Shanelle invested $10,000, and at the end of 1...Ch. 4.4 - Prob. 16PECh. 4.4 - Prob. 17PECh. 4.4 - 18. Blake has a total of $4000 to invest in two...Ch. 4.4 - Prob. 19PECh. 4.4 - Prob. 20PECh. 4.4 - How much 50% disinfectant solution must be mixed...Ch. 4.4 - Prob. 22PECh. 4.4 - 23. How much 45% disinfectant solution must be...Ch. 4.4 - Prob. 24PECh. 4.4 - Prob. 25PECh. 4.4 - Prob. 26PECh. 4.4 - Prob. 27PECh. 4.4 - Silvia wants to mix a 40% apple juice drink with...Ch. 4.4 - Prob. 29PECh. 4.4 - Prob. 30PECh. 4.4 - Prob. 31PECh. 4.4 - A plane flies 720 mi with the wind in 3 hr. The...Ch. 4.4 - Prob. 33PECh. 4.4 - Prob. 34PECh. 4.4 - Debi has $2.80 in a collection of dimes and...Ch. 4.4 - Prob. 36PECh. 4.4 - Prob. 37PECh. 4.4 - Prob. 38PECh. 4.4 - In the 1961–1962 NBA basketball season, Wilt...Ch. 4.4 - 40. In the 1971–1972 NBA basketball season, Kareem...Ch. 4.4 - Prob. 41PECh. 4.4 - Prob. 42PECh. 4.4 - A total of $60,000 is invested in two accounts,...Ch. 4.4 - Prob. 44PECh. 4.4 - Prob. 45PECh. 4.4 - Prob. 46PECh. 4.4 - Prob. 47PECh. 4.4 - Prob. 48PECh. 4.4 - Prob. 49PECh. 4.4 - Prob. 50PECh. 4.5 - Solve the system. x + 2 y + z = 1 3 x − y + 2 z =...Ch. 4.5 - Prob. 2SPCh. 4.5 - Prob. 3SPCh. 4.5 - Prob. 4SPCh. 4.5 - Prob. 1PECh. 4.5 - Prob. 2PECh. 4.5 - Which of the following points are solutions to the...Ch. 4.5 - Prob. 4PECh. 4.5 - Prob. 5PECh. 4.5 - Prob. 6PECh. 4.5 - For Exercises 11–34, solve the system of...Ch. 4.5 - For Exercises 11–34, solve the system of...Ch. 4.5 - Prob. 9PECh. 4.5 - Prob. 10PECh. 4.5 - Prob. 11PECh. 4.5 - For Exercises 11–34, solve the system of...Ch. 4.5 - Prob. 13PECh. 4.5 - Prob. 14PECh. 4.5 - Prob. 15PECh. 4.5 - Prob. 16PECh. 4.5 - Prob. 17PECh. 4.5 - Prob. 18PECh. 4.5 - Prob. 19PECh. 4.5 - Prob. 20PECh. 4.5 - Prob. 21PECh. 4.5 - For Exercises 11–34, solve the system of...Ch. 4.5 - For Exercises 11–34, solve the system of...Ch. 4.5 - For Exercises 11–34, solve the system of...Ch. 4.5 - For Exercises 11–34, solve the system of...Ch. 4.5 - For Exercises 11–34, solve the system of...Ch. 4.5 - Prob. 27PECh. 4.5 - Prob. 28PECh. 4.5 - For Exercises 11–34, solve the system of...Ch. 4.5 - Prob. 30PECh. 4.5 - Prob. 31PECh. 4.5 - Prob. 32PECh. 4.5 - Prob. 33PECh. 4.5 - Prob. 34PECh. 4.5 - Prob. 35PECh. 4.5 - Prob. 36PECh. 4.5 - Prob. 37PECh. 4.5 - Prob. 38PECh. 4.5 - For Exercises 35–46, solve the system. If there is...Ch. 4.5 - Prob. 40PECh. 4.5 - Prob. 41PECh. 4.5 - Prob. 42PECh. 4.5 - Prob. 43PECh. 4.5 - Prob. 44PECh. 4.5 - Prob. 45PECh. 4.5 - Prob. 46PECh. 4.6 - 1. The perimeter of a triangle is 30 in. The...Ch. 4.6 - Annette, Barb, and Carlita work in a clothing...Ch. 4.6 - Prob. 1PECh. 4.6 - Prob. 2PECh. 4.6 - One angle of a triangle measures 6° more than...Ch. 4.6 - Prob. 4PECh. 4.6 - Prob. 5PECh. 4.6 - 10. The perimeter of a triangle is 5 ft. The...Ch. 4.6 - Prob. 7PECh. 4.6 - Prob. 8PECh. 4.6 - Prob. 9PECh. 4.6 - Prob. 10PECh. 4.6 - Prob. 11PECh. 4.6 - Prob. 12PECh. 4.6 - Prob. 13PECh. 4.6 - Prob. 14PECh. 4.6 - Prob. 15PECh. 4.6 - Prob. 16PECh. 4.6 - Prob. 17PECh. 4.6 - Souvenir hats, T-shirts, and jackets are sold at a...Ch. 4.6 - Prob. 19PECh. 4.6 - Prob. 20PECh. 4 - For Exercises 1–4, determine if the ordered pair...Ch. 4 - Prob. 2RECh. 4 - Prob. 3RECh. 4 - Prob. 4RECh. 4 - Prob. 5RECh. 4 - Prob. 6RECh. 4 - Prob. 7RECh. 4 - Prob. 8RECh. 4 - Prob. 9RECh. 4 - Prob. 10RECh. 4 - For Exercises 11–18, solve the system by graphing....Ch. 4 - For Exercises 11–18, solve the system by graphing....Ch. 4 - Prob. 13RECh. 4 - Prob. 14RECh. 4 - Prob. 15RECh. 4 - Prob. 16RECh. 4 - For Exercises 11–18, solve the system by graphing....Ch. 4 - Prob. 18RECh. 4 - Prob. 19RECh. 4 - Prob. 20RECh. 4 - Prob. 21RECh. 4 - Prob. 22RECh. 4 - Prob. 23RECh. 4 - Prob. 24RECh. 4 - 25. Given the system: a. Which variable from...Ch. 4 - Prob. 26RECh. 4 - Prob. 27RECh. 4 - Prob. 28RECh. 4 - Prob. 29RECh. 4 - Prob. 30RECh. 4 - Prob. 31RECh. 4 - Prob. 32RECh. 4 - Prob. 33RECh. 4 - Given the system. 3 x − 5 y = 1 2 x − y = − 4 a....Ch. 4 - Prob. 35RECh. 4 - Prob. 36RECh. 4 - Prob. 37RECh. 4 - Prob. 38RECh. 4 - Prob. 39RECh. 4 - Prob. 40RECh. 4 - Prob. 41RECh. 4 - Prob. 42RECh. 4 - Prob. 43RECh. 4 - Prob. 44RECh. 4 - Prob. 45RECh. 4 - Prob. 46RECh. 4 - Prob. 47RECh. 4 - Prob. 48RECh. 4 - Prob. 49RECh. 4 - Prob. 50RECh. 4 - Prob. 51RECh. 4 - Prob. 52RECh. 4 - For Exercises 53–58, solve the systems of...Ch. 4 - For Exercises 53–58, solve the systems of...Ch. 4 - For Exercises 53–58, solve the systems of...Ch. 4 - Prob. 56RECh. 4 - Prob. 57RECh. 4 - For Exercises 53–58, solve the systems of...Ch. 4 - Prob. 59RECh. 4 - Prob. 60RECh. 4 - Prob. 61RECh. 4 - 62. In a triangle, the largest angle measures 76°...Ch. 4 - Prob. 1TCh. 4 - Prob. 2TCh. 4 - Prob. 3TCh. 4 - Prob. 4TCh. 4 - Prob. 5TCh. 4 - Prob. 6TCh. 4 - Prob. 7TCh. 4 - 8. a. How many solutions does a system of two...Ch. 4 - Prob. 9TCh. 4 - For Exercises 9–14, solve each system using any...Ch. 4 - For Exercises 9–14, solve each system using any...Ch. 4 - Prob. 12TCh. 4 - Prob. 13TCh. 4 - Prob. 14TCh. 4 - Prob. 15TCh. 4 - Prob. 16TCh. 4 - Prob. 17TCh. 4 - Prob. 18TCh. 4 - 19. A plane travels 910 mi in 2 hr against the...Ch. 4 - Prob. 20TCh. 4 - Prob. 21TCh. 4 - Prob. 22TCh. 4 - Prob. 23TCh. 4 - Prob. 24TCh. 4 - Prob. 25TCh. 4 - Prob. 26TCh. 4 - Prob. 27T
Knowledge Booster
Background pattern image
Algebra
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, algebra and related others by exploring similar questions and additional content below.
Similar questions
SEE MORE QUESTIONS
Recommended textbooks for you
Text book image
College Algebra (MindTap Course List)
Algebra
ISBN:9781305652231
Author:R. David Gustafson, Jeff Hughes
Publisher:Cengage Learning
Text book image
Big Ideas Math A Bridge To Success Algebra 1: Stu...
Algebra
ISBN:9781680331141
Author:HOUGHTON MIFFLIN HARCOURT
Publisher:Houghton Mifflin Harcourt
Text book image
Algebra and Trigonometry (MindTap Course List)
Algebra
ISBN:9781305071742
Author:James Stewart, Lothar Redlin, Saleem Watson
Publisher:Cengage Learning
Text book image
College Algebra
Algebra
ISBN:9781305115545
Author:James Stewart, Lothar Redlin, Saleem Watson
Publisher:Cengage Learning
Text book image
Glencoe Algebra 1, Student Edition, 9780079039897...
Algebra
ISBN:9780079039897
Author:Carter
Publisher:McGraw Hill
Text book image
Algebra & Trigonometry with Analytic Geometry
Algebra
ISBN:9781133382119
Author:Swokowski
Publisher:Cengage
SEE MORE TEXTBOOKS
Matrix Factorization - Numberphile; Author: Numberphile;https://www.youtube.com/watch?v=wTUSz-HSaBg;License: Standard YouTube License, CC-BY