4. Using the technique shown in class today for working with geometric sums, give the closed form for the following. Notice that the lower bound this time is one (not zero): 500 10-3' i=1 5. Now extend that approach to come up with a closed form for the following, where a1 and r are simply arbitrary constants: 7t a1 T 6. Similarly, come up with a closed form for the following, noting that the upper and lower bounds have changed: 1 a1 i-0