Question

求使方程组 X+Y=M+2 4X+5Y=6M+3的解X,Y都是正数的M的取值范围

要详细过程

Answer 1

|x+y=m+2
|4x+5y=6m+3
由上可得
|4x+4y=4m+8
|4x+5y=6m+3
解之得
x=-m+7
y=2m-5
因为x、y均为正数
x=-m+7>0
m<7
y=2m-5>0
m>5/2
则5/2<m<7

Answer 2

解：由方程组x+y=m+24x+5y=6m+3解得x=-m+7y=2m-5
∵x，y均为正数
∴-m+7＞02m-5＞0解这个不等式组得：5/2＜m＜7答：m的取值范围是5/2＜m＜7

Answer 3

X+Y=M+2 ①
4X+5Y=6M+3②
4×①-②=4x+4y-4x-5y=4m+8-6m-3
=>y=2m-5>0
=>m>5/2
①×5-②=5x+5y-4x-5y=5m+10-6m-3
=>x=-m+7>0
=>m<7
=>5/2<m<7

Answer 4

x,y都是正数
=>
(6m+3)/4>m+2>(6m+3)/5
=>
2.5<m<7

Answer 5

2008-10-30 21:45X+Y=M+2 ①
4X+5Y=6M+3②
4×①-②=4x+4y-4x-5y=4m+8-6m-3
=>y=2m-5>0
=>m>5/2
①×5-②=5x+5y-4x-5y=5m+10-6m-3
=>x=-m+7>0
=>m<7
=>5/2<m<7