Question

化简求值[(x+0.5y)^2+(x-0.5y)^2](2x^2-0.5y^2),其中x=-3,y=4.

Answer 1

[(x+0.5y)^2+(x-0.5y)^2](2x^2-0.5y^2)

=[(x^2+xy+0.25y^2)+(x^2-xy+0.25y^2)](2x^2-0.5y^2)

=(2x^2+0.5y^2)(2x^2-0.5y^2)

=(2x^2)^2-(0.5y^2)^2

=4x^4-(1/4)y^4

将x=-3,y=4代入

原式=4*（-3）^4-(1/4)*(4)^4=260