(x+y)(x-y)+(x-y)平方-(x-y)(3x-y) 其中x=-2 y=3分之一

问题描述:

(x+y)(x-y)+(x-y)平方-(x-y)(3x-y) 其中x=-2 y=3分之一

(x+y)(x-y)+(x-y)平方-(x-y)(3x-y)
=(x-y)(x+y+x-y-3x+y)
=(x-y)(-x+y)
=-(x-y)²
=-(-2-3分之一)²
=-(-3分之7)²
=-9分之49