Question

已知(a-1)^2+|b+3|=0,求2(-a^2+3ab-1/2b^2)-4(-2a^2+4ab-b^2)的值

Answer 1

2(-a^2+3ab-1/2b^2)-4(-2a^2+4ab-b^2)

=-2a^2+6ab-b^2+8a^2-16ab+4b^2

=6a^2-10ab+3b^2

(a-1)^2+|b+3|=0

a-1=0 b+3=0

a=1 b=-3

代入前面式子得

=6x1^2-10x1x（-3）+3x（-3）^2

=6+30+27

=63