Question

find the sum of first 15terms of an A.P 2,7,12​

Answer 1

Answer:

10/7

Step-by-step explanation:

a+(n-1) d

15:2+7n-7

15:-5+7n

10:7n

10/7:n

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Answer 2

Answer:

a=2, d=5

Sn=n/2[2a+(n-1)d]

S15= 15/2[2×2+(15-1)5]

=15/2[4+70]

=15/2×74

=15×37

=555

Therefore,

S15=> 555