问题
解答题
(1)计算:(
(2)先化简再求值:(3x+1)(3x-1)-(3x+1)2,其中x=
|
答案
(1)原式=2+1-3+2×1 2
=1;
(2)原式=9x2-1-(9x2+6x+1)
=9x2-1-9x2-6x-1
=-6x-2,
当x=
时,原式=-1-2=-3.1 6
(1)计算:(
(2)先化简再求值:(3x+1)(3x-1)-(3x+1)2,其中x=
|
(1)原式=2+1-3+2×1 2
=1;
(2)原式=9x2-1-(9x2+6x+1)
=9x2-1-9x2-6x-1
=-6x-2,
当x=
时,原式=-1-2=-3.1 6