$f(x)$ is increasing when $f'(x)>0$

$⇒f'(x)=0$

$⇒12x(4x^2-1)=0$

$⇒12x(2x-1)(2x+1)=0$

∴ f(x) is increasing when,

$x∈\left(-\frac{1}{2},0\right)∪\left(\frac{1}{2},∞\right)$