Question

x的平方-2{1/2x的平方-【(x+5)+2(x的平方-6)】+4x的平方},其中x=-2

Answer 1

原式=x²-2[1/2x²-(x+5+2x²-12)+4x²]

=x²-2(1/2x²-x-5-2x²+12+4x²)

=x²-x²+2x+10+4x²-24-8x²

=(x²-x²+4x²-8x²)+2x+(10-24)

=-4x²+2x-14

当x=-2时

原式=-4×(-2)²+2×(-2)-14

=-4×4-4-14

=-16-18

=-34