The chain rule and logarithms practice question 11

The logarithm is applied to $x^{2} + 4$, not to $x$. What does that inside contribute when you differentiate?

$\dfrac{d}{dx}\log(u) = \dfrac{u'}{u}$. Identify $u$ first.

Here $u = x^{2} + 4$, so $u' = 2x$.