问题
解答题
(1)计算:
(2)先化简,再求值:(
|
答案
(1)原式=3+(-8)-
×2
+1 (4分)2 2
=3-8-1+1
=-5. (5分)
(2)原式=
•3x(x+1)-x(x-1) (x+1)(x-1)
(1分)(x+1)(x-1) 2x
=
(2分)3x2+3x-x2+x 2x
=2x2+4x 2x
=
(3分)2x(x+2) 2x
=x+2. (4分)
当x=-3时,
原式=-3+2=-1. (5分)