# What is the second derivative of f(x)=15x^3-23x^2+9x-1 ?

Dec 20, 2015

$f ' ' \left(x\right) = 90 x - 46$

#### Explanation:

The main thing to know here is that $\frac{d}{\mathrm{dx}} \left[{x}^{n}\right] = n {x}^{n - 1}$.

$f \left(x\right) = 15 {x}^{3} - 23 {x}^{2} + 9 x - 1$

$f ' \left(x\right) = 45 {x}^{2} - 46 x + 9$

$f ' ' \left(x\right) = 90 x - 46$