



 
Hi Autumn, To evaluate $f(x  h)$ look at the expression for $f(x)$ and replace $x$ everywhere you see it by $x  h.$ $f(x  h)$ then becomes \[\frac{x  h}{\left((x  h)^2  f(x)\right)}.\] Expand the denominator and then write down $f(x  h)  f(x).$ This is the difference of two fractions so you need to find a common denominator and rewrite $f(x  h)  f(x)$ with this denominator. Simplify. If you do this correctly you will see that the numerator of the rewritten $f(x  h)  f(x)$ has a common factor of $h$ which will cancel with the denominator of \[\frac{f(x  h)  f(x)}{h}\] as long as $h \neq 0.$ Penny  


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