Nature of Mathematics (MindTap Course List)
Nature of Mathematics (MindTap Course List)
13th Edition
ISBN: 9781133947257
Author: karl J. smith
Publisher: Cengage Learning
bartleby

Videos

Question
Book Icon
Chapter 5.6, Problem 3PS
To determine

To explain:

The identity property.

Blurred answer
Students have asked these similar questions
how to construct the following same table?
The following is known. The complete graph K2t on an even number of vertices has a 1- factorization (equivalently, its edges can be colored with 2t - 1 colors so that the edges incident to each vertex are distinct). This implies that the complete graph K2t+1 on an odd number of vertices has a factorization into copies of tK2 + K₁ (a matching plus an isolated vertex). A group of 10 people wants to set up a 45 week tennis schedule playing doubles, each week, the players will form 5 pairs. One of the pairs will not play, the other 4 pairs will each play one doubles match, two of the pairs playing each other and the other two pairs playing each other. Set up a schedule with the following constraints: Each pair of players is a doubles team exactly 4 times; during those 4 matches they see each other player exactly once; no two doubles teams play each other more than once. (a) Find a schedule. Hint - think about breaking the 45 weeks into 9 blocks of 5 weeks. Use factorizations of complete…
. The two person game of slither is played on a graph. Players 1 and 2 take turns, building a path in the graph. To start, Player 1 picks a vertex. Player 2 then picks an edge incident to the vertex. Then, starting with Player 1, players alternate turns, picking a vertex not already selected that is adjacent to one of the ends of the path created so far. The first player who cannot select a vertex loses. (This happens when all neighbors of the end vertices of the path are on the path.) Prove that Player 2 has a winning strategy if the graph has a perfect matching and Player 1 has a winning strategy if the graph does not have a perfect matching. In each case describe a strategy for the winning player that guarantees that they will always be able to select a vertex. The strategy will be based on using a maximum matching to decide the next choice, and will, for one of the cases involve using the fact that maximality means no augmenting paths. Warning, the game slither is often described…

Chapter 5 Solutions

Nature of Mathematics (MindTap Course List)

Ch. 5.1 - Prob. 11PSCh. 5.1 - Prob. 12PSCh. 5.1 - Prob. 13PSCh. 5.1 - Prob. 14PSCh. 5.1 - Prob. 15PSCh. 5.1 - Prob. 16PSCh. 5.1 - Prob. 17PSCh. 5.1 - Prob. 18PSCh. 5.1 - Prob. 19PSCh. 5.1 - Prob. 20PSCh. 5.1 - Prob. 21PSCh. 5.1 - Level 1 In Problems 15-26, classify each as an...Ch. 5.1 - Prob. 23PSCh. 5.1 - Prob. 24PSCh. 5.1 - Prob. 25PSCh. 5.1 - Prob. 26PSCh. 5.1 - Prob. 27PSCh. 5.1 - Prob. 28PSCh. 5.1 - Prob. 29PSCh. 5.1 - Level 1 Think of three nonassociative word triples...Ch. 5.1 - Prob. 31PSCh. 5.1 - Prob. 32PSCh. 5.1 - Prob. 33PSCh. 5.1 - Prob. 34PSCh. 5.1 - Prob. 35PSCh. 5.1 - Prob. 36PSCh. 5.1 - Prob. 37PSCh. 5.1 - Prob. 38PSCh. 5.1 - Prob. 39PSCh. 5.1 - Prob. 40PSCh. 5.1 - Prob. 41PSCh. 5.1 - Prob. 42PSCh. 5.1 - Prob. 43PSCh. 5.1 - Prob. 44PSCh. 5.1 - Prob. 45PSCh. 5.1 - Prob. 46PSCh. 5.1 - Prob. 47PSCh. 5.1 - Prob. 48PSCh. 5.1 - Prob. 49PSCh. 5.1 - Prob. 50PSCh. 5.1 - Prob. 51PSCh. 5.1 - Prob. 52PSCh. 5.1 - Prob. 53PSCh. 5.1 - Prob. 54PSCh. 5.1 - Prob. 55PSCh. 5.1 - Problem Solving Level 3 Consider a soldier facing...Ch. 5.1 - Prob. 57PSCh. 5.1 - Prob. 58PSCh. 5.1 - Prob. 59PSCh. 5.1 - Problem Solving Level 3 60. The Vanishing...Ch. 5.2 - IN YOUR OWN WORDS What is a prime number?Ch. 5.2 - Prob. 2PSCh. 5.2 - Prob. 3PSCh. 5.2 - Prob. 4PSCh. 5.2 - Prob. 5PSCh. 5.2 - Prob. 6PSCh. 5.2 - Prob. 7PSCh. 5.2 - Prob. 8PSCh. 5.2 - Prob. 9PSCh. 5.2 - Prob. 10PSCh. 5.2 - Prob. 11PSCh. 5.2 - Prob. 12PSCh. 5.2 - Prob. 13PSCh. 5.2 - Prob. 14PSCh. 5.2 - Find all the prime numbers less than or equal to...Ch. 5.2 - Determine the largest prime you need to consider...Ch. 5.2 - Prob. 17PSCh. 5.2 - Prob. 18PSCh. 5.2 - Prob. 19PSCh. 5.2 - Prob. 20PSCh. 5.2 - Prob. 21PSCh. 5.2 - Prob. 22PSCh. 5.2 - Prob. 23PSCh. 5.2 - Prob. 24PSCh. 5.2 - Prob. 25PSCh. 5.2 - Prob. 26PSCh. 5.2 - Prob. 27PSCh. 5.2 - Prob. 28PSCh. 5.2 - Prob. 29PSCh. 5.2 - Prob. 30PSCh. 5.2 - Prob. 31PSCh. 5.2 - Prob. 32PSCh. 5.2 - Prob. 33PSCh. 5.2 - Prob. 34PSCh. 5.2 - Prob. 35PSCh. 5.2 - Prob. 36PSCh. 5.2 - Prob. 37PSCh. 5.2 - Prob. 38PSCh. 5.2 - Prob. 39PSCh. 5.2 - Two movie theaters, UAI and UAII, start their...Ch. 5.2 - Prob. 41PSCh. 5.2 - Shannon is planning a party and wants to give each...Ch. 5.2 - Boxes that are 12 inches tall are stacked next to...Ch. 5.2 - Hot dogs come in packages of 10, while buns come...Ch. 5.2 - IN YOUR OWN WORDS We used a sieve of Eratosthenes...Ch. 5.2 - Prob. 46PSCh. 5.2 - Prob. 47PSCh. 5.2 - Prob. 48PSCh. 5.2 - Prob. 49PSCh. 5.2 - Prob. 50PSCh. 5.2 - Prob. 51PSCh. 5.2 - Prob. 52PSCh. 5.2 - Prob. 53PSCh. 5.2 - Prob. 54PSCh. 5.2 - Prob. 55PSCh. 5.2 - What is the smallest natural number that is...Ch. 5.2 - Prob. 57PSCh. 5.2 - Prob. 58PSCh. 5.2 - Prob. 59PSCh. 5.2 - Prob. 60PSCh. 5.3 - Prob. 1PSCh. 5.3 - Prob. 2PSCh. 5.3 - Prob. 3PSCh. 5.3 - Prob. 4PSCh. 5.3 - Prob. 5PSCh. 5.3 - Prob. 6PSCh. 5.3 - Prob. 7PSCh. 5.3 - Prob. 8PSCh. 5.3 - Prob. 9PSCh. 5.3 - Prob. 10PSCh. 5.3 - Prob. 11PSCh. 5.3 - Prob. 12PSCh. 5.3 - Prob. 13PSCh. 5.3 - Prob. 14PSCh. 5.3 - Prob. 15PSCh. 5.3 - Prob. 16PSCh. 5.3 - Prob. 17PSCh. 5.3 - Prob. 18PSCh. 5.3 - Prob. 19PSCh. 5.3 - Simplify the expressions in Problems 9-37. a....Ch. 5.3 - Prob. 21PSCh. 5.3 - Prob. 22PSCh. 5.3 - Prob. 23PSCh. 5.3 - Prob. 24PSCh. 5.3 - Prob. 25PSCh. 5.3 - Prob. 26PSCh. 5.3 - Prob. 27PSCh. 5.3 - Prob. 28PSCh. 5.3 - Prob. 29PSCh. 5.3 - Prob. 30PSCh. 5.3 - Prob. 31PSCh. 5.3 - Prob. 32PSCh. 5.3 - Prob. 33PSCh. 5.3 - Prob. 34PSCh. 5.3 - Prob. 35PSCh. 5.3 - Prob. 36PSCh. 5.3 - Prob. 37PSCh. 5.3 - Prob. 38PSCh. 5.3 - Prob. 39PSCh. 5.3 - Prob. 40PSCh. 5.3 - Prob. 41PSCh. 5.3 - Prob. 42PSCh. 5.3 - Prob. 43PSCh. 5.3 - Prob. 44PSCh. 5.3 - Prob. 45PSCh. 5.3 - Prob. 46PSCh. 5.3 - Prob. 47PSCh. 5.3 - Prob. 48PSCh. 5.3 - Prob. 49PSCh. 5.3 - Prob. 50PSCh. 5.3 - Prob. 51PSCh. 5.3 - Prob. 52PSCh. 5.3 - Perform the indicated operations. Let k be a...Ch. 5.3 - Perform the indicated operations. Let k be a...Ch. 5.3 - a. State the commutative property. b. Is ...Ch. 5.3 - Prob. 56PSCh. 5.3 - Prob. 57PSCh. 5.3 - Prob. 58PSCh. 5.3 - Multiply 1,234,5679,999,999 a. using a calculator...Ch. 5.3 - Prob. 60PSCh. 5.4 - IN YOUR OWN WORDS What does it mean for a fraction...Ch. 5.4 - IN YOUR OWN WORDS Describe the process for...Ch. 5.4 - Prob. 3PSCh. 5.4 - Prob. 4PSCh. 5.4 - IN YOUR OWN WORDS Use algebra to show where the...Ch. 5.4 - IN YOUR OWN WORDS Use algebra to show where the...Ch. 5.4 - Completely reduce the fractions in Problems 7-18....Ch. 5.4 - Completely reduce the fractions in Problems 7-18....Ch. 5.4 - Completely reduce the fractions in Problems 7-18....Ch. 5.4 - Completely reduce the fractions in Problems 7-18....Ch. 5.4 - Completely reduce the fractions in problem 7-18....Ch. 5.4 - Completely reduce the fractions in problem 7-18....Ch. 5.4 - Completely reduce the fractions in problem 7-18....Ch. 5.4 - Completely reduce the fractions in problem 7-18....Ch. 5.4 - Completely reduce the fractions in problem 7-18....Ch. 5.4 - Completely reduce the fractions in problem 7-18....Ch. 5.4 - Completely reduce the fractions in problem 7-18....Ch. 5.4 - Completely reduce the fractions in problem 7-18....Ch. 5.4 - Perform the indicated operations in problems...Ch. 5.4 - Perform the indicated operations in problems...Ch. 5.4 - Perform the indicated operations in problems...Ch. 5.4 - Perform the indicated operations in problems...Ch. 5.4 - Perform the indicated operations in problems...Ch. 5.4 - Prob. 24PSCh. 5.4 - Prob. 25PSCh. 5.4 - Prob. 26PSCh. 5.4 - Prob. 27PSCh. 5.4 - Prob. 28PSCh. 5.4 - Prob. 29PSCh. 5.4 - Prob. 30PSCh. 5.4 - Prob. 31PSCh. 5.4 - Prob. 32PSCh. 5.4 - Prob. 33PSCh. 5.4 - Prob. 34PSCh. 5.4 - Prob. 35PSCh. 5.4 - Prob. 36PSCh. 5.4 - Prob. 37PSCh. 5.4 - Prob. 38PSCh. 5.4 - Prob. 39PSCh. 5.4 - Prob. 40PSCh. 5.4 - Prob. 41PSCh. 5.4 - Prob. 42PSCh. 5.4 - Prob. 43PSCh. 5.4 - Prob. 44PSCh. 5.4 - Perform the indicated operations in problems...Ch. 5.4 - Perform the indicated operations in problems...Ch. 5.4 - Prob. 47PSCh. 5.4 - Prob. 48PSCh. 5.4 - Prob. 49PSCh. 5.4 - Prob. 50PSCh. 5.4 - Prob. 51PSCh. 5.4 - Prob. 52PSCh. 5.4 - Prob. 53PSCh. 5.4 - Prob. 54PSCh. 5.4 - Prob. 55PSCh. 5.4 - Prob. 56PSCh. 5.4 - Prob. 57PSCh. 5.4 - Prob. 58PSCh. 5.4 - Prob. 59PSCh. 5.4 - Prob. 60PSCh. 5.5 - Prob. 1PSCh. 5.5 - Prob. 2PSCh. 5.5 - Prob. 3PSCh. 5.5 - Prob. 4PSCh. 5.5 - Prob. 5PSCh. 5.5 - Prob. 6PSCh. 5.5 - Prob. 7PSCh. 5.5 - Prob. 8PSCh. 5.5 - Prob. 9PSCh. 5.5 - Prob. 10PSCh. 5.5 - Prob. 11PSCh. 5.5 - Prob. 12PSCh. 5.5 - Prob. 13PSCh. 5.5 - Prob. 14PSCh. 5.5 - Prob. 15PSCh. 5.5 - Prob. 16PSCh. 5.5 - Prob. 17PSCh. 5.5 - Prob. 18PSCh. 5.5 - Prob. 19PSCh. 5.5 - Prob. 20PSCh. 5.5 - Prob. 21PSCh. 5.5 - Prob. 22PSCh. 5.5 - Prob. 23PSCh. 5.5 - Prob. 24PSCh. 5.5 - Prob. 25PSCh. 5.5 - Prob. 26PSCh. 5.5 - Prob. 27PSCh. 5.5 - Prob. 28PSCh. 5.5 - Prob. 29PSCh. 5.5 - Prob. 30PSCh. 5.5 - Prob. 31PSCh. 5.5 - Prob. 32PSCh. 5.5 - Prob. 33PSCh. 5.5 - Prob. 34PSCh. 5.5 - Prob. 35PSCh. 5.5 - Prob. 36PSCh. 5.5 - Prob. 37PSCh. 5.5 - Prob. 38PSCh. 5.5 - If a carpenter wants to make sure that the corner...Ch. 5.5 - Prob. 40PSCh. 5.5 - An antenna is to be erected and held by guy wires....Ch. 5.5 - Prob. 42PSCh. 5.5 - Prob. 43PSCh. 5.5 - Prob. 44PSCh. 5.5 - Prob. 45PSCh. 5.5 - Prob. 46PSCh. 5.5 - Prob. 47PSCh. 5.5 - Prob. 48PSCh. 5.5 - Prob. 49PSCh. 5.5 - Prob. 50PSCh. 5.5 - Prob. 51PSCh. 5.5 - Prob. 52PSCh. 5.5 - Prob. 53PSCh. 5.5 - Prob. 54PSCh. 5.5 - Prob. 55PSCh. 5.5 - Prob. 56PSCh. 5.5 - Prob. 57PSCh. 5.5 - Prob. 58PSCh. 5.5 - Prob. 59PSCh. 5.5 - Prob. 60PSCh. 5.6 - Prob. 1PSCh. 5.6 - Prob. 2PSCh. 5.6 - Prob. 3PSCh. 5.6 - Prob. 4PSCh. 5.6 - Prob. 5PSCh. 5.6 - Prob. 6PSCh. 5.6 - Prob. 7PSCh. 5.6 - Tell whether each number is an element of N a...Ch. 5.6 - Prob. 9PSCh. 5.6 - Prob. 10PSCh. 5.6 - Express each of the numbers in Problems 9-12 as a...Ch. 5.6 - Prob. 12PSCh. 5.6 - Prob. 13PSCh. 5.6 - Prob. 14PSCh. 5.6 - Prob. 15PSCh. 5.6 - Prob. 16PSCh. 5.6 - Prob. 17PSCh. 5.6 - Prob. 18PSCh. 5.6 - Prob. 19PSCh. 5.6 - Prob. 20PSCh. 5.6 - Prob. 21PSCh. 5.6 - Prob. 22PSCh. 5.6 - Prob. 23PSCh. 5.6 - Prob. 24PSCh. 5.6 - Prob. 25PSCh. 5.6 - Carry out the operations with decimal forms in...Ch. 5.6 - Prob. 27PSCh. 5.6 - Prob. 28PSCh. 5.6 - Prob. 29PSCh. 5.6 - Prob. 30PSCh. 5.6 - Prob. 31PSCh. 5.6 - Prob. 32PSCh. 5.6 - Prob. 33PSCh. 5.6 - Prob. 34PSCh. 5.6 - Prob. 35PSCh. 5.6 - Prob. 36PSCh. 5.6 - Prob. 37PSCh. 5.6 - Prob. 38PSCh. 5.6 - Prob. 39PSCh. 5.6 - Prob. 40PSCh. 5.6 - Prob. 41PSCh. 5.6 - Prob. 42PSCh. 5.6 - Prob. 43PSCh. 5.6 - Prob. 44PSCh. 5.6 - Prob. 45PSCh. 5.6 - Prob. 46PSCh. 5.6 - Prob. 47PSCh. 5.6 - Prob. 48PSCh. 5.6 - Prob. 49PSCh. 5.6 - Prob. 50PSCh. 5.6 - Prob. 51PSCh. 5.6 - Prob. 52PSCh. 5.6 - Prob. 53PSCh. 5.6 - Prob. 54PSCh. 5.6 - Prob. 55PSCh. 5.6 - Let be an arbitrary operation in Problems 52-59....Ch. 5.6 - Let be an arbitrary operation in Problems 52-59....Ch. 5.6 - Prob. 58PSCh. 5.6 - Prob. 59PSCh. 5.6 - Prob. 60PSCh. 5.7 - Level 1. IN YOUR OWN WORDS. What do we mean by...Ch. 5.7 - Prob. 2PSCh. 5.7 - Prob. 3PSCh. 5.7 - Prob. 4PSCh. 5.7 - Prob. 5PSCh. 5.7 - Prob. 6PSCh. 5.7 - Level 1. Perform the indicated operations in...Ch. 5.7 - Prob. 8PSCh. 5.7 - Prob. 9PSCh. 5.7 - Prob. 10PSCh. 5.7 - Prob. 11PSCh. 5.7 - Prob. 12PSCh. 5.7 - Prob. 13PSCh. 5.7 - Prob. 14PSCh. 5.7 - Prob. 15PSCh. 5.7 - Prob. 16PSCh. 5.7 - Prob. 17PSCh. 5.7 - Prob. 18PSCh. 5.7 - Prob. 19PSCh. 5.7 - Prob. 20PSCh. 5.7 - Prob. 21PSCh. 5.7 - Prob. 22PSCh. 5.7 - Prob. 23PSCh. 5.7 - Prob. 24PSCh. 5.7 - Prob. 25PSCh. 5.7 - Prob. 26PSCh. 5.7 - Prob. 27PSCh. 5.7 - Prob. 28PSCh. 5.7 - Prob. 29PSCh. 5.7 - Prob. 30PSCh. 5.7 - Prob. 31PSCh. 5.7 - Prob. 32PSCh. 5.7 - Prob. 33PSCh. 5.7 - Prob. 34PSCh. 5.7 - Prob. 35PSCh. 5.7 - Level 2. If you know that your aunt in Problem 34...Ch. 5.7 - Prob. 37PSCh. 5.7 - Prob. 38PSCh. 5.7 - Prob. 39PSCh. 5.7 - Prob. 40PSCh. 5.7 - Prob. 41PSCh. 5.7 - Prob. 42PSCh. 5.7 - Prob. 43PSCh. 5.7 - Prob. 44PSCh. 5.7 - Prob. 45PSCh. 5.7 - Prob. 46PSCh. 5.7 - Prob. 47PSCh. 5.7 - Prob. 48PSCh. 5.7 - Prob. 49PSCh. 5.7 - Prob. 50PSCh. 5.7 - Prob. 51PSCh. 5.7 - Prob. 52PSCh. 5.7 - Prob. 53PSCh. 5.7 - Prob. 54PSCh. 5.7 - Prob. 55PSCh. 5.7 - Prob. 56PSCh. 5.7 - Prob. 57PSCh. 5.7 - Prob. 58PSCh. 5.7 - Prob. 59PSCh. 5.7 - Prob. 60PSCh. 5.8 - Prob. 1PSCh. 5.8 - Prob. 2PSCh. 5.8 - Prob. 3PSCh. 5.8 - Prob. 4PSCh. 5.8 - Prob. 5PSCh. 5.8 - Prob. 6PSCh. 5.8 - Prob. 7PSCh. 5.8 - Prob. 8PSCh. 5.8 - Prob. 9PSCh. 5.8 - Number the letters of the alphabet from 1 to 26;...Ch. 5.8 - Prob. 11PSCh. 5.8 - Prob. 12PSCh. 5.8 - Prob. 13PSCh. 5.8 - Prob. 14PSCh. 5.8 - Prob. 15PSCh. 5.8 - Prob. 16PSCh. 5.8 - Prob. 17PSCh. 5.8 - Prob. 18PSCh. 5.8 - Prob. 19PSCh. 5.8 - Prob. 20PSCh. 5.8 - Prob. 21PSCh. 5.8 - Prob. 22PSCh. 5.8 - Prob. 23PSCh. 5.8 - Prob. 24PSCh. 5.8 - Prob. 25PSCh. 5.8 - Prob. 26PSCh. 5.8 - Prob. 27PSCh. 5.8 - Prob. 28PSCh. 5.8 - Prob. 29PSCh. 5.8 - Prob. 30PSCh. 5.8 - Prob. 31PSCh. 5.8 - Give the decoding key for the encoding keys in...Ch. 5.8 - Prob. 33PSCh. 5.8 - Prob. 34PSCh. 5.8 - Prob. 35PSCh. 5.8 - Prob. 36PSCh. 5.8 - Prob. 37PSCh. 5.8 - Prob. 38PSCh. 5.8 - Prob. 39PSCh. 5.8 - Use Figure 5.25 to encode or decode the messages...Ch. 5.8 - Prob. 41PSCh. 5.8 - Prob. 42PSCh. 5.8 - Prob. 43PSCh. 5.8 - Prob. 44PSCh. 5.8 - Prob. 45PSCh. 5.8 - Prob. 46PSCh. 5.8 - Prob. 47PSCh. 5.8 - Prob. 48PSCh. 5.8 - Prob. 51PSCh. 5.8 - Prob. 52PSCh. 5.8 - Prob. 53PSCh. 5.8 - Prob. 54PSCh. 5.8 - Prob. 55PSCh. 5.8 - Prob. 56PSCh. 5.8 - Prob. 57PSCh. 5.8 - Prob. 58PSCh. 5.8 - Prob. 59PSCh. 5.8 - Prob. 60PSCh. 5.CR - Prob. 1CRCh. 5.CR - Prob. 2CRCh. 5.CR - Prob. 3CRCh. 5.CR - Prob. 4CRCh. 5.CR - Reduce each fraction. If it is reduced, so state....Ch. 5.CR - Prob. 6CRCh. 5.CR - Prob. 7CRCh. 5.CR - Prob. 8CRCh. 5.CR - Prob. 9CRCh. 5.CR - Prob. 10CRCh. 5.CR - Prob. 11CRCh. 5.CR - Prob. 12CRCh. 5.CR - Prob. 13CRCh. 5.CR - Prob. 14CRCh. 5.CR - Prob. 15CRCh. 5.CR - Prob. 16CRCh. 5.CR - Prob. 17CRCh. 5.CR - Do You Weigh Too Much? In the United States, an...Ch. 5.CR - Prob. 19CRCh. 5.CR - Prob. 20CR
Knowledge Booster
Background pattern image
Math
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
SEE MORE QUESTIONS
Recommended textbooks for you
  • Text book image
    Algebra: Structure And Method, Book 1
    Algebra
    ISBN:9780395977224
    Author:Richard G. Brown, Mary P. Dolciani, Robert H. Sorgenfrey, William L. Cole
    Publisher:McDougal Littell
    Text book image
    PREALGEBRA
    Algebra
    ISBN:9781938168994
    Author:OpenStax
    Publisher:OpenStax
Text book image
Algebra: Structure And Method, Book 1
Algebra
ISBN:9780395977224
Author:Richard G. Brown, Mary P. Dolciani, Robert H. Sorgenfrey, William L. Cole
Publisher:McDougal Littell
Text book image
PREALGEBRA
Algebra
ISBN:9781938168994
Author:OpenStax
Publisher:OpenStax
Double and Half Angle Formulas | Analytic Trig | Pre-Calculus; Author: Brian McLogan;https://www.youtube.com/watch?v=eTdKgsyCmHs;License: Standard YouTube License, CC-BY