Why is this true: $(4+t^2)\frac{dy}{dt}+2ty= \frac{d}{dt}[(4+t^2)y]$

Question

I'm looking at a solution to a problem in my textbook and one of the steps is giving me issues. It states that:

$(4+t^2)\frac{dy}{dt}+2ty= \frac{d}{dt}[(4+t^2)y]$

Can anyone explain how this is true? Thanks!

Answer 1

Use product rule.

$((4+t^2)y)' = (4+t^2)' y + (4+t^2) y'$