/sci/ - Science & Math

Why is the answer

[math]
-\frac{1}{2m-5}
[/math]

wrong?

Solution was:

[math]
... = \frac{-(2m-5)}{(2m-5)^2} = -\frac{1}{2m-5}
[/math]

proper solution:
[math]
... = \frac{(5-2m)}{(2m-5)^2} = \frac{(5-2m)}{(5-2m)^2} = \frac{1}{5-2m}
[/math]