Question

数学好的进来下咯！

m为何值时，关于XY的方程组MX-Y-5=0,2X+3MY-7=0的解满足X>0,Y<0

Answer 1

3M^2X-3MY-15M=0

(3M^2+2)X=15M+7
(3M^2+2)X=(15M+7)/(3M^2+2)>0
15M+7>0
M>-7/15

2MX+3M^2Y-7M=0
2MX-2Y-10=0
(3M^2+2)Y=7M-10
7M-10<0
M<10/7

-7/15<M<10/7

Answer 2

MX-Y-5=0
2X+3MY-7=0
解得
X=(15M+7)/(3M^2+2)>0
Y=(7M-10)/(3M^2+2)<0
再解就行了