Question
need help with #38 step by step.
ers 3, The sum Sns given and an is described in Exercise 1 is is the llll where a s. the 4) is and the last term se 1 4, The first term of S (6i 5. The first three terms of (5i 3) are S and The common difference is In Erercises 23-34, write a formula for the general term (the nth term) of each arithmeric sequence Do nor use a recursion formula Then use the formula for an ro find a the 20th term of the sequence 24. 2.7, 12, 17. 23, 1.5, 9, 13, 26, 6. 1. -4, -9... 25, 7, 3, -1, -5 28. a1 9, d 30, a 1 -70, d -5 29, a -20, -4 32, a an-1 5, a 1 6 3, a1 31. a 33, an an-1 10, a 30 34. an am-1 12, a1 24 35. Find the sum of the first 20 terms of the arithmetic sequence: 4, 10, 16, 22, 30. Find the sum of the first 25 terms of the arithmetic sequence: 7, 19, 31,43, 37. Find the sum of the first 50 terms of the arithmetic sequence -10,-6, -2,2, 38. Find the sum of the first 50 terms of the arithmetic sequence -15, -9, -3, 3 39. Find 1 2 3 4 100, the sum of the first 100 natural numbers. 40. Find 2 4 6 8 200, the sum of the first 100 positive even integers.
Explanation / Answer
the given AP is -15 , - 9 , -3 3 --------
te first term is a= -15 , common difference d= -9 -(-15) = 15-9=6
sum of n terms of an AP is [n (2a+(n-1)d)] /2 where a is the first term and d is the common difference
S50 = 50 [ - 30 + 49 x6] /2
= 6600
