# How do you differentiate g(y) =(4x-5)(x-5)  using the product rule?

Feb 8, 2017

$g ' \left(y\right) = 8 x - 25$

#### Explanation:

The product is not needed to differentiate this functions as we can expand it easily. We should use the power rule instead.

$g \left(y\right) = \left(4 x - 5\right) \left(x - 5\right) = 4 {x}^{2} - 25 x - 25$

Power rule:

$\frac{d}{\mathrm{dx}} \left(a {x}^{n}\right) = a n {x}^{n - 1}$

$g ' \left(y\right) = 8 x - 25$