Compute n if "P₂ =240. Show all the steps! \text { Expand by applying the Binomial theorem: }\left(\frac{3 x}{4}-\frac{7 y}{5}\right)^{3} \text { Determine the coefficient of } \frac{1}{x^{2}} \text { in the binomial expansion of }\left(2 x^{2}-\frac{1}{x}\right)^{14} \text {. }