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
÷6 3 1 2
=5
×3
×6 3 2
=10;
(2)
-4 4- 11
-4
-11 7 2 3+ 7
=
-4(4+
)11 5
-4(
+11
)7 4 2(3-
)7 2
=
+16 5
-4 11 5
-11
-3+7 7
=
-1 5
;9 11 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± 64 2
,4±8 2
∴x1=6,x2=-2