So I am given the following question:

> 
> Suppose 
>  $$\lim \_{x\to 25}\frac{\sqrt{x}-5}{ax+b} = \frac{1}{40}$$ 
>  Find $a$ and $b$.
> 
> 
> 

I'm not exactly what to do from here, but what I did was multiplying $$\frac{\sqrt{x}-5}{ax+b}$$ by its conjugate 
($\frac{ax-b}{ax-b}$), resulting in 
$$\frac{100a}{625a^2-b^2} = \frac{1}{40}$$
Now I'm stuck and not sure what to do from here. Am I on a correct track?