Question

Find the sum of first seven terms of an AP whose first term is 5 and seventh term is 23.

Answer 1

Step-by-step explanation:

s7=n/2(a7-a1)

=7/2(23-5)

7/2(18)

9×7

63

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Answer 2

Step-by-step explanation:

Sn = n/2 (a+l)

= 3.5(28)