Asked by Anonymous

If f(x)=the sqrt of 3x,find f'(3).

Isn't it 3/2•sqrt of 3?
Answered by Steve
If f = √u, f' = u' / 2√u.
You have u=3x, so

f'(x) = 3 / 2√(3x)
f'(3) = 3 / 2√9 = 1/2