Derivative and horizontal tangent help

[kings13]

Derivative and horizontal tangent help!

Determine the point at which the graph of the function has a horizontal tangent line.

http://www.webassign.net/cgi-bin/symimage.cgi?expr=f(x) = (8 x**2)/(x**2+8)


and f(x)=x/ root2x-1endroot

 

[dreit]

Try rewriting the function (8x^2/x^2+8) as (8x^2)(x^2+8)^-1 and then try to take your derivative.

 

[dreit]

Or if you do not plan on using chain rule for your derivative, you can keep the function how it is and just use quotient rule.