Question

2) If the first term of A.P.is -3 and 10th term is 15
find S10
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Answer 1

Answer:

HERE A¹ = -3 , A ¹⁰ = 15 , N = 10

SUM OF A.P = 10/2 (-3 + 15) = 5 *12 = 60

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Answer 2

a= -3

t10=15

tn=a+(n-1)×d

t10=-3+(n-1)×d

15=-3+(n-1)d

15+3=(n-1)d

18=dn-d