Find $\displaystyle (\frac{r_1}{|r_2| } )' $for$\displaystyle r_1 = ti + {t}^{ 2} j - 3tk $and $\displaystyle r_2 = {t}^{ 2}i - 2j + tk $

I have found $\displaystyle |r_2| = \sqrt{{t}^{ 4} + {t}^{2 } + 4 } $

But now when i differntaite i do not get there answer of

$\displaystyle

\frac{4-{t}^{4}i}{({t}^{ 4} + {t}^{2 } + 4)^\frac{3}{2 }} }+ \frac{{t}^{3}+ 8tj}{({t}^{ 4} + {t}^{2 } + 4)^\frac{3}{2 }} + \frac{3({t}^{4}-4k}{({t}^{ 4} + {t}^{2 } + 4)^\frac{3}{2 } }

$