<p>I don't remember the exact numbers of the question, but it was something like this...</p>
<p>If r(x)=5x+2 and s(r(x))=2x-10 , then what is s(x)?
a) 2x+8
b) blah
c) blah
and so on</p>
<p>I know I can just plug any number for x and find the answer, but is there a proper or a "mathematical" way to do this?</p>
<p>Yeah, all you do divide the s(r)(X) function by the r(x) function. It's just composite functions in reverse</p>
<p>Okay that's probably not a good way of saying it... It's kinda hard to explain this but: basically you find the difference between 2x-10 and 5x+2 and you add that to x. For example, f(x)=3 and f(s(x))=5. If we wanted to find s(x), it would be x+2 because after we plug 3 for x, the diff. between f(s(x) is 2.</p>
<p>and if you forget how to do it..</p>
<p>just plug and chug :D (the answer into the problem, i'm saying)</p>