一、(-5x+2y)(-2y+5x)

问题描述:

一、(-5x+2y)(-2y+5x)
二、[(-x-1/4y)^2+(x-1/4y)^2](2x^2-1/8y^2)
三、化简求值;(-2x-3)(2x-3)+(3x-2)^2+(x+1)(x+3),其中X=-1
四、已知a-b=3,ab=4,求a^2+b^2的值和a^2-b^2的值

1.(-5x+2y)(-2y+5x) =-(5x-2y)(5x-2y)=-(5x-2y)^2=-(25x^2-20xy+4y^2)=20xy-25x^2-4y^22.[(-x-1/4y)^2+(x-1/4y)^2](2x^2-1/8y^2) =[(x+1/4y)^2+(x-1/4y)^2](2x^2-1/8y^2) =(x^2+1/2y+1/16y^2+x^2-1/2y+1/16y^2)(2x^2...