Question

the sum of the series in a. p. is 81/2,the common difference is 5/2 and last term is 13find the first term and the number of terms in the series​

Answer 1

Answer:

last term is 13

then a+(n-1) d=13 eq. 1

a+5n/2 -5/2=13

a+5n/2 =31/2

2a+5n =31 eq. 2

1/2n{2a+(n-1) d} =81/2

then

n(a+13) =81 eq. 3

by solving the eq.

it is solved

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