y = $ \lim_{ x \rightarrow 3} \left ( \frac{ x^{4} - 81 } { 2 x^{2} -5x -3 } \right )$
= $\lim_{ x \rightarrow 3} \left ( \frac{(x^{2})^{2}-9^{2}}{2x^{2}-5x-3}\right )$
= $\lim_{ x \rightarrow 3} \left (\frac{(x-3)(x+3)(x^{2}+9)}{(2x+1)(x-3)}\right )$
= $\lim_{ x \rightarrow 3} \left (\frac{(x+3)(x^{2}+9)}{(2x+1)}\right )$
= $\left ( \frac{(3+3)(3^{2}+9)}{(2*3 +1)} \right )$
= $\left ( \frac{6*18}{7} \right )$
=$ \left ( \frac{108 } { 7 } \right )$