6. (a) (3 points) Use the General Binomial Theorem to calculate the Maclaurin series for f(u) = (1 + u) -2, and find its radius of convergence. (b) (4 points) Using the previous part and the fact n e n! n= (radius of convergence = co), determine only the first four coefficients in the Maclaurin series for 1 (1 + 4x2)2 ed and give a lower bound on its radius of convergence