Question

m为何值时,代数式2m-3分之5m-1的值与代数式2分之7-m的值的和大5

Answer 1

(5m-1)/(2m-3)+(7-m)/2=5
(2m-3)(7-m)+10m-2=10(2m-3)
10m-2+14m-21-2m²+3m=20m-30
10m-2m²-23=20m-30
7m-2m²+7=0
2m²-7m-7=0
m²-7/2m-7/2=0
解得：m=（7+√105）/4或 m=(7-√105）／4

追问

是大5不是等于5.。。。

追答

求m的取值范围吗？

追问

是的

追答

(5m-1)/(2m-3)+(7-m)/2＞5

2（5m-1）+（2m-3)(7-m)＞20m-30
10m-2+14m-2m^2-21+3m-20m+30＞0
-2m^2+7m+7＞0
2m^2-7m-7＜0
解得 (7-√105）／4＜m＜（7+√105）/4