If y = (2x + 1)3, find dydx

If y = (2x + 1)3, find $\frac{dy}{dx}$

Answer Details

If y = (2x + 1)3, then
Let u = 2x + 1 so that, y = u3
$\frac{dy}{du}$ = 3u2 and $\frac{dy}{dx}$ = 2
Hence by the chain rule,
$\frac{dy}{dx}$ = $\frac{dy}{du}$ x $\frac{du}{dx}$
= 3u2 x 2
= 6u2
= 6(2x + 1)2