Determine the radius of convergence of the power series

Question

a. Does the series _n=1Σ^∞ (n - √n) / (n² + √n) converge or diverge?

b. Determine the radius of convergence of the power series _n=1Σ^∞ (-1)ⁿ (3ⁿ / n4ⁿ) xⁿ.

c. Show that the power series converges for x = 4/3.

d. Determine the sum of the power series =1Σ^∞ n(n - 1)(-3/4)ⁿ.