4) The graph of y = (x)/(1+25x^2) for x is greater than or equal to 0 has a horizontal tangent at x = what.
So what I did was find the first derivative. I did the quotient rule and ended up with
x50x - 1+25x^2
---------------
(1+25x^2)^2
I equated that with 0 but I don't know how to solve for x without using a calculator. Someone please help.