# Math Help - Rational function values

1. ## Rational function values

Hi,

Having a little problem on this..

A rational function g(x) = a / (b+x) is such that g(x) = f(x) wherever f is defined.

Find the values of a and b

f(x) = (12-4x) / (x^2+2x-15)

2. ## Re: Rational function values

\displaystyle \begin{align*} f(x) &= \frac{12 - 4x}{x^2 + 2x - 15} \\ &= \frac{-4(x - 3)}{(x + 5)(x - 3)} \\ &= \frac{-4}{x + 5} \end{align*}

So a = -4 and b = 5.