20f2 Exercise 4 (5 pt) Reminding that, if an is a geometric sequence with common ration r 75 1, then YI 1 - 1! S" := zak = L") k=l calculate the following 5 z 53-k k=0 n-l : 910k k=0 Exercise 5 (8 pt) The second term of n geometric senenee is 6 and the third one. is with p 96 2. Find the common ratio and the sum, assuming that the sum of the first three term is 36