先化简,再求值:(x-1)(x-2)-3x(x+3)+2(x+2)(x-1),其中x=1/3.
问题描述:
先化简,再求值:(x-1)(x-2)-3x(x+3)+2(x+2)(x-1),其中x=
. 1 3
答
(x-1)(x-2)-3x(x+3)+2(x+2)(x-1)
=x2-3x+2-3x2-9x+2(x2+x-2)
=x2-3x+2-3x2-9x+2x2+2x-4
=-10x-2,
当x=
时,原式=-1 3
.16 3