Question

the sum of the series in AP is 81÷2 the common difference is 5÷2 and the last term is 13 . find the first term and the number of terms in the series

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Answer 1

Answer:

(21)^2 i.e. (13+8)^2 or [square of 21].

Step-by-step explanation:

as, 5=2+3, 3=1+2, 8=5+3, 13=8+5 and so on. so your answer will be (21)^2 i.e. (13+8)^2 or [square of 21]. 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

Answer 2

Answer:

Answer is

a=1/2 and n=6

Step-by-step explanation:

the answer is in those two pictures

hope it helps you