Question

Find the sum of 2,7,12..... to 10 terms
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Answer 1

Answer:

Here a=2 ,d=7-2=5 n=10

now, S10=10/2[2(2)+(10-1)5]

=5[4+45]

=5×49 = 245

Answer 2

Answer:

a=2

n=10

d=a1-a2

7-2=5

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

=10/2{2×2+(10-1)5}

=5{4+(9)5}

=5{4+45}

=5(49)

Sn=245