Derivative Problem

[LadyBoots]

I have to find the derivative of -20x / (x^2 - 9)^2, but I cant figure it out. I know its the quotient rule, I know what the quotient rule is, and I know the final answer because I have the solution manual. But I dont know how to get here. Whatever I do, it just doesnt make sense.

Any help is appreciated.

 

[tkhunny]

Pretty hard to tell what you did if you don't show us anything.

\(\displaystyle \frac{(x^{2}-9)^{2}\cdot (-20) - (-20x)\cdot (2(x^{2}-9)(2x))}{(x^{2}-9)^{4}}\)

I'm going to guess with absolutely no information that you can follow the rule and you managed to get this far. Did you remember all the Chain Rule in the second part of the numerator?

There might be a little alegbra after that.