7. A tree farm initially has 4000 trees. Each year 20% of the trees are harvested (removed), and 600 seedlings (young trees) are planted. (a) Write a recursive rule for the number of trees on this tree farm. Make sure that your rule is complete. (b) Calculate how many trees remain on the farm after 4 years. EVES 8. Find a formula, Sn, for the following series. Also, find S,, S2, S3, SA, and Soo . Show all work, and simplify your formula for full credit. sumlin to songupee yarwollon she isbidding -2 +2+6+10+14+... + an 9. Find a formula, Sn, for the following series. Also, find S,, S2, S3, S4, and S83 . Show all work, and simplify your formula for full credit. For the last sum, find the exact value and the approximation. - V3+ 2V3 + 573+ 8 73 +... + an 10. What is the formula for the sum of a Geometric Series? Once you have written down the formula, use it to find the 10th partial sum for a Geometric Series that starts with 2 and has a common ration (r value) of 0.5