Write in Standard Form 5m^2n+9n^3-mn^2+2m^3

$5 m^{2} n + 9 n^{3} - m n^{2} + 2 m^{3}$

To write a polynomial in standard form, simplify and then arrange the terms in descending order.

$a x^{2} + b x + c$

Move $9 n^{3}$ .

$5 m^{2} n - m n^{2} + 2 m^{3} + 9 n^{3}$

Move $- m n^{2}$ .

$5 m^{2} n + 2 m^{3} - m n^{2} + 9 n^{3}$

Reorder $5 m^{2} n$ and $2 m^{3}$ .

$2 m^{3} + 5 m^{2} n - m n^{2} + 9 n^{3}$