exercise - differentiation but messy

worked example: Differentiate $f(x)=(3x^2+1)\sqrt{1-3x}$

$f^{\prime }(x)=(6x)(\sqrt{1-3x})+(3x^2+1)(\frac{1}{2}\cdot (1-3x{)}^{-\frac{1}{2}}\cdot (-3))$

$f^{\prime }(x)=6x\sqrt{1-3x}+(3x^2+1)\frac{1}{2\sqrt{1-3x}}\cdot -3$

$f^{\prime }(x)=6x\sqrt{1-3x}-\frac{3(3x^2+1)}{2\sqrt{1-3x}}$