(1)解方程:3x2-6x+1=0;(2)化简求值:x2-1x2+2x+1•12x-2,其中x=-12.-数学

题目简介

(1)解方程:3x2-6x+1=0;(2)化简求值:x2-1x2+2x+1•12x-2,其中x=-12.-数学

题目详情

(1)解方程:3x2-6x+1=0;
(2)化简求值:
x2-1
x2+2x+1
1
2x-2
,其中x=-
1
2
题型:解答题难度:中档来源:山西

答案

(1)3x2-6x+1=0.这里a=3,b=-6,c=1.△=b2-4ac=36-12=24>0;
x=
-b±
b2-4ac
2a

=
24
2×3

=
6
3

即x1=
3+
6
3
,x2=
3-
6
3

(2)
x2-1
x2+2x+1
class="stub"1
2x-2

=
(x+1)(x-1)
(x+1)2
class="stub"1
2(x-1)

=class="stub"1
2(x+1)
(或class="stub"1
2x+2
);
当x=-class="stub"1
2
时,原式=class="stub"1
2(x+1)
=class="stub"1
2(-class="stub"1
2
+1)
=1

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