计算:(1)a2(a-1)+(a-5)(a+7);(2)(x-5y)2-(x+5y)2;(3)[(ab+1)(ab-1)-2a2b2+1]÷(-ab).-数学

题目简介

计算:(1)a2(a-1)+(a-5)(a+7);(2)(x-5y)2-(x+5y)2;(3)[(ab+1)(ab-1)-2a2b2+1]÷(-ab).-数学

题目详情

计算:
(1)a2(a-1)+(a-5)(a+7);
(2)(x-5y)2-(x+5y)2
(3)[(ab+1)(ab-1)-2a2b2+1]÷(-ab).
题型:解答题难度:中档来源:不详

答案

(1)a2(a-1)+(a-5)(a+7),
=a3-a2+a2+7a-5a-35,
=a3+2a-35;

(2)(x-5y)2-(x+5y)2,
=(x-5y+x+5y)(x-5y-x-5y),
=-20xy;

(3)[(ab+1)(ab-1)-2a2b2+1]÷(-ab),
=(a2b2-1-2a2b2+1)÷(-ab),
=ab.

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