Q. 154.7( 6 Votes )

If the sum of fir

Answer :

Let us assume the 1st term be a and common differed be d

It is given in the question that,


S7 = 49 and =S17 = 289


We know that, .


.


.


2a + 6d = 14 (i)


Also, .


2a + 16d = 34 (ii)


Now, by solving (i) and (ii) we get:


-0d = - 20


d = 2


tting the value of d in (i), we get:


2a + 12 = 14


= 2


a = 1




.


.


Hence, Proved.

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