我们知道,平方差公式为(a+b)(a-b)=a~2-b~2,巧妙运用平方差公式来解题可以起到化繁为简、化难为易的作用.一、巧变位置例1计算:(2m+3n)(3n-2m)解:原式=(3n+2m)(3n-2m)=(3n)~2-(2m)~2=9n~2-4m~2二、巧变符号例2计算:(2a-3b)(-2a-3b)解:原式=-(2a-3b)(2a+36)=-[(2a)~2-(3b)~2]=-(4a~2-9b~2)=-4a~2+9b~2 We know that the formula for the square deviation is (a + b) (ab) = a ~ 2-b ~ 2, clever use of the square difference formula to solve the problem can play a complex and easy, (2n + 2m) (3n-2m) = (3n) ~ 2- (2m) ~ 2 = 9n ~ 2-4m ~ 2 Second, the complex symbols Example 2 Calculation: (2a-3b) (-2a-3b) Solution: the original = - (2a-3b) (2a +36) = - [(2a) ~ 2- (3b) ~ 2 ] = - (4a ~ 2-9b ~ 2) = - 4a ~ 2 + 9b ~ 2