If the constant term in the binomial expansion of ${\left({\mathrm{x}}^2-\frac{1}{\mathrm{x}}\right)}^{\mathrm{n}},\mathrm{n}\in \mathrm{N}$ is 15, then the value of n is equal to ___________.

$\begin{array}{l}{\mathrm{T}}_{\mathrm{r}+1}{=}^{\mathrm{n}}{\mathrm{C}}_{\mathrm{r}}{\left({\mathrm{x}}^2\right)}^{\mathrm{n}-\mathrm{r}}(-1{)}^{\mathrm{r}}{\mathrm{x}}^{-\mathrm{r}}\\ {=}^{\mathrm{n}}{\mathrm{C}}_{\mathrm{r}}{\mathrm{x}}^{2\mathrm{n}-3\mathrm{r}}(-1{)}^{\mathrm{r}}\end{array}$

Constant term${=}^{\mathrm{n}}{\mathrm{C}}_{\mathrm{r}}(-1{)}^{\mathrm{r}}\text{ if }2\mathrm{n}=3\mathrm{r}$

i.e., coefficient of x = 0

Hence, ${ }^{\mathrm{n}}{\mathrm{C}}_{2\mathrm{n}/3}(-1{)}^{2\mathrm{n}/3}=15{=}^6{\mathrm{C}}_4$

$\Rightarrow \mathrm{n}=6$