Derivative

[ace123]

The question is Find the derivative of:
y= (ax + sqrt of x^2 + b^2)^-2

I got this

-2(ax + sqrt of x^2 + b^2)^-3 *(a+ 2/ sqrt of x^2 + b^2) *2x

but i dno if this is right, can someone help me.

[PowerIso]

Yea I got the same thing minus 2/ sqrt of x^2 + b^2

It should be 1/(2*biggiantmess^1/2)

or u^1/2 = 1/(2*u^1/2)