2.8.68 Power Series

Condition: put the functions into the steppe rows according to degrees \ (x \) using standard decays. Indicate the intervals of their convergence. a) \ (f (x) = x^{2} \ cos \ left (\ frac {3 x} {4} \ right) \) \ (f (x) = \ frac {11 x} {11 x+7} \)