Find dy/dx for y=3tan^-1(x/2).

Question

I know the answer is 6/x^2+4 but I'm stuck at y'=3(1/1+(x/2)^2)(1/2)

Answer 1

so far, so good ...
dy/dx = 3/(1+(x/2)^2) * 1/2
= 3/[2(1+x^2/4)]
= 3/[8(x^2+4)]