Who is good at Maths?Come in!
来源:百度知道 编辑:UC知道 时间:2024/06/27 14:36:22
数学高手们,小弟有几道题不怎么理解.请高手们指点迷津:
(1)若不等式(a+2)X>a+2的解集为X<1,则a的取值范围是?
(2)不等式组x+9<5X+1和x>m+1的解集是x>2,则m的取值范围是?
(3)已知方程组x+2y=3和2x+ay=b,当等a于多少,b等于多少时,方程有无数解.
高手们,请把解题过程写出来,小弟必定感激不尽.
(1)若不等式(a+2)X>a+2的解集为X<1,则a的取值范围是?
(2)不等式组x+9<5X+1和x>m+1的解集是x>2,则m的取值范围是?
(3)已知方程组x+2y=3和2x+ay=b,当等a于多少,b等于多少时,方程有无数解.
高手们,请把解题过程写出来,小弟必定感激不尽.
1.把左边展开,合并同类项提出a
2.左边解出x>2,所以m+1<2
3.当成直线方程 左边y=-(1/2)x+3/2 右边y=-(2/a)x+b/a
方程有无数解说明两直线重合,所以两方程相同,对应项系数相等
you get lost.
为什么会发在英文区,还以为SAT数学之类的
RUBBISH
1.a<0
(a+2)x>a+2
ax+2x>a+2
a(x-1)>2-2x
∵x<1 ∴2-2x>0 x-1<0
∴a(x-1)>0 ∴a<0
2.无解吧?
3.这题只要方程符合直线方程就行了
所以只要a不等于-2就可以了
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