Answer
$-2n^{4}-n^{3}+n^{2}$
Work Step by Step
We are given the polynomial $n^{4}-2n^{3}+n^{2}-3n^{4}+n^{3}$.
We can use the distributive property to combine like terms.
$n^{4}-2n^{3}+n^{2}-3n^{4}+n^{3}=(1-3)n^{4}+(-2+1)n^{3}+n^{2}=(-2)n^{4}+(-1)n^{3}+n^{2}=-2n^{4}-n^{3}+n^{2}$
