Binomial Theorem - Coefficients in Products of Binomial Expansions

By considering the general term in the binomial expansion of \({{\left( 2{{x}^{2}}-\frac{1}{x} \right)}^{7}}\), explain why there are only three terms of negative powers of \(x\) in this expansion.

Find the term independent of \(x\) in the expansion of \({{\left( 3x-{{x}^{2}} \right)}^{2}}{{\left( 2{{x}^{2}}-\frac{1}{x} \right)}^{7}}\).