计算: ①(a+b)(a-2b)-(a+2b)(a-b) ②5x(x2+2x+1)-(2x+3)(x-5)

问题描述:

计算:
①(a+b)(a-2b)-(a+2b)(a-b)   
②5x(x2+2x+1)-(2x+3)(x-5)

①原式=a2-2ab+ab-2b2-a2+ab-2ab+2b2=-2ab;                         ②原式=5x...