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由众所周知的完全平方公式:a~2+2ab+ b~2=(a+b)~2,a~2-2ab+b~2=(a-b)~2,可得ab=(a+b)~2-(a-b)~2/4.(※)这是一个非常重要的恒等式,它浅显、简单,便于记忆.对于解一类与两数的和(差)、积
From the well-known complete square formula: a ~ 2 + 2ab + b ~ 2 = (a + b) ~ 2 and a ~ 2-2ab + b ~ 2 = 2- (ab) ~ 2 / 4. (*) This is a very important identity, it is simple, easy to remember. For solving a class and the sum of two (difference), product