calculus question

Question

Determine the point(s) at which the graph of f(x) = -3/(sqrrt(2x-1)) has a horizontal tangent.

Answer 1

y = -3 (2x-1)^(-1/2)

y' = (3/2)(2x-1)^(-3/2)(2) = f'(x)

= 3(2x-1)^(-3/2)

the function is always increasing so the derivative is never zero