2x2-[x2-2(x2-3x-1)-3(x2-1-2x)]其中:x=1/2.
问题描述:
2x2-[x2-2(x2-3x-1)-3(x2-1-2x)]其中:x=
. 1 2
答
原式=2x2-(x2-2x2+6x+2-3x2+3+6x)
=2x2-(-4x2+12x+5)
=6x2-12x-5
∵x=
,1 2
代入原式可得:6×
-12×1 4
-5=-1 2
.19 2