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posted by Jenny Friday, May 3, 2013 at 3:40pm.
To square 75, one can multiply (70)(80) and add 25 to that product. Can someone explain how this would work, without calculating?
since a^2-b^2 = (a-b)(a+b) a^2 = (a-b)(a+b)+b^2 75^2 = (75-5)(75+5)+5^2 = (70)(80)+25
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