问题
解答题
(1)计算:(-2)2-5×
(2)计算:
(3)解方程组:
|
答案
(1)原式=4-1+2×
=4;1 2
(2)原式=
•a a-1
-(a+1)(a-1) a(a-1)
=1 a-1
-a+1 a-1
=1 a-1
;a a-1
(3)
,x+y=1 ① 2x+y=3 ②
②-①得x=2,
将x=2代入①,得y=-1,
∴原方程组的解为:
.x=2 y=-1
(1)计算:(-2)2-5×
(2)计算:
(3)解方程组:
|
(1)原式=4-1+2×
=4;1 2
(2)原式=
•a a-1
-(a+1)(a-1) a(a-1)
=1 a-1
-a+1 a-1
=1 a-1
;a a-1
(3)
,x+y=1 ① 2x+y=3 ②
②-①得x=2,
将x=2代入①,得y=-1,
∴原方程组的解为:
.x=2 y=-1