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Perfect SquareThe term perfect square is used in mathematics in two meanings: - a positive integer which is the square of some other integer, i.e. can be written in the form n2 for some integer n.
- an algebraic expression that can be factored as the square of some other expression, e.g. a2 ± 2ab + b2 = (a ± b)2. (see Square (algebra)).
This is not the same as a magic square. Using differences of squares as multiplication Integer multiplication can be done entirely by a difference of two squares. Examples: -
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In general, the product of two numbers is equal to the square of their average minus their difference from the average squared. A geometric constructive "proof" of this relation is shown the following animation: The starting rectangle is A by B. The resulting large square is length (A+B)/2, and the smaller gray square (remainder being subtracted) is length |A-B|/2. Using this relation, you can multiply relatively large nearly equal numbers more quickly if you memorize a relatively small list of squares. If you're multiplying an even by an odd, you can avoid "halves" by adjust one number, by requiring one more addition at the end -
Example: -
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