Find the derivative of the function $f(x)$ = $3(x^4 - 1)( 5x^2 + 2x)$

The correct answer is $3(30x^5 + 10x^4 - 10x - 2)$

Following the Constant rule and the Product rule we can write

$f ' (x)$ = $3[(x^4 - 1)(10x + 2) + ( 5x^2 + 2x)(4x^3)]$

= $3(10x^5 + 2x^4 - 10x - 2 + 20x^5 + 8x^4)$

= $3(30x^5 + 10x^4 - 10x - 2)$