Question

若(2x-y)的2次方+|y+2|=0,求代数式2[(x-y)的二次方+(x+y)(x-y)]的值

Answer 1

(2x-y)的2次方+|y+2|=0
2x-y=0，y+2=0
x=-1，y=-2

2[(x-y)^2+(x+y)(x-y)]
=2(x^2-2xy+y^2+x^2-y^2)
=2(2x^2-2xy)
=4x^2-4xy
=4-4×(-1)×(-2)
=4-8
=-4