If $\displaystyle x$ is real , prove that the expression $\displaystyle \frac{(x - a)(x - c)}{(x -b)} $ is capable of assuming all values provided that $\displaystyle a , b , c$ are either in ascending or descending orders of magnitude .

I'm lost.......how do I show that $\displaystyle \frac{(x - a)(x - c)}{(x -b)} $ is "capable of assuming all values".