问题
解答题
(1)先化简,再求值:
(2)解方程:x2-3x-1=0. |
答案
(1)原式=
÷x-2 (x+1)(x-1)
+2(x+1) (x+1)2
,1 x-1
=
•x-2 (x+1)(x-1)
+(x+1)2 2(x+1)
,1 x-1
=
+x-2 2(x-1)
,1 x-1
=
,x 2(x-1)
=
,x 2x-2
当x=
+1时,2
原式=
=
+ 12 2
+2-22
=
+12 2 2
=(
+ 1)•2 2 2
• 2 2
;2+ 2 4
(2)∵a=1,b=-3,c=-1,
∴b2-4ac=(-3)2-4×1×(-1)=13,
∴x=
=3± 13 2×1
,3± 13 2
∴x1=
,x2=3+ 13 2
.3- 13 2