The 5th term of an ap is -3 its common difference is -4. What is the sum of its first 10 terms?

Answer 1

a + 4d = -3
You know d, so you can find a=13
S10 = 10/2 (2a + 9d) = 5(2*13 + 9*-4) = -50

or, since a+4d = -3 and d = -4, a+5d = -7
S10 = 10/2 (a+4d + a+5d) = 5(-3 + -7) = -50

Answer 2

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