Question

Calculate the difference between the sums of the first 20 terms of the arithmetic sequence 15,10,14..?

Answer 1

Answer:

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Answer 2

Answer:

Given AP = 15, 10, 14, .......

So, a = 15, d = 10 - 15 = -5

n = 20

Sum of first 20 terms = n/2[2a(n-1)d]

                                   = 20/2[2 X 20(20-1)-5]

                                   = 10(40 X 19 - 5) )

                                   = 10(40 X 14)

                                   = 10 X 56 = 560

Step-by-step explanation:

Hope it helps u friend