4. Rewrite the geometric series using the sigma notation and calculate the value of the sum. w 9 27 81 1 + + + ... 5 25 125 625 5. Find all values of x for which the geometric series converges and find its sum. OO E(2x - 3)k K=0 6. Calculate the value of the partial sum for S4 and S5, find a formula for general partial sum Sn, and then find the limit of Sn as n approaches infinity. 00 1 K=3 k+2 k+1_