计算:
(1)(2a-5)(-2a-5);
(2);
(3)(5ab-3x)(-3x-5ab);
(4);
(5).
网友回答
解:(1)(2a-5)(-2a-5)=25-4a2;
(2)(+)(-)=;
(3)(5ab-3x)(-3x-5ab)=9x2-25a2b2;
(4)()()-(x+8),
=-4--2x,
=-2x-4;
(5)(x-y)()-()(),
=(x-y)()-(),
=.
解析分析:根据平方差公式(a+b)(a-b)=a2-b2,即可解答本题.
点评:本题考查了平方差公式,属于基础题,关键是掌握平方差公式(a+b)(a-b)=a2-b2.