1. ## Third derivative

I need to find the third derivative of 16 squareroot x at 4

I've gotten to the first derivative which I think equals 16/2 square root x?
I used product rule to get this and I'm assuming that I need to keep using product rule and not chain rule?

Thanks

2. Originally Posted by johnf124
I need to find the third derivative of 16 squareroot x at 4

I've gotten to the first derivative which I think equals 16/2 square root x?
I used product rule to get this and I'm assuming that I need to keep using product rule and not chain rule?

Thanks
power rule the whole way ...

$y = 16x^{\frac{1}{2}}$

$y' = 8x^{-\frac{1}{2}}$

$y'' = -4x^{-\frac{3}{2}}$

$y''' = 6x^{-\frac{5}{2}}$