I was just wondering if I was on the right way. I have this function that I need to find the domain f(x)=-7/2x+5
I think the domain would be (-infinity, -5/2) u (-5/2, infinity)
If the function is $\displaystyle f(x)=\frac{-7}{2x+5}$ then your answer is correct.
But please, please learn to post correctly.
You could at least use grouping symbols.