问题
解答题
(1)化简:
(2)
(3)解方程:(x-1)(x+3)=5; (4)x2-4x-12=0(用求根公式). |
答案
(1)
75 |
| ||
3 |
1 | ||
|
=5
3 |
| ||
3 |
2 |
=10;
(2)
4 | ||
4-
|
4 | ||||
|
2 | ||
3+
|
=
4(4+
| ||
5 |
4(
| ||||
4 |
2(3-
| ||
2 |
=
16 |
5 |
4
| ||
5 |
11 |
7 |
7 |
=
1 |
5 |
9
| ||
5 |
(3)(x-1)(x+3)=5,
x2+2x-3=5,
x2+2x-8=0,
(x+4)(x-2)=0,
x+4=0或x-2=0,
x1=-4,x2=2;
(4)x2-4x-12=0,
∵a=1,b=-4,c=-12,
b2-4ac=16-4×1×(-12)=64>0,
∴x=
4±
| ||
2 |
4±8 |
2 |
∴x1=6,x2=-2