Question

find the sum of first 25 terms of an ap whose n th term is a=5+6n​

Answer 1

Answer:

Find the sum of first 25 terms of an AP whose nth term is given by tn = 2 - 3n

Solution:

Put n =1

put n =2

put n =3

So, A.P. become s: -1 , -4 , -7, ........

So, first term =a= -1

Common difference d = -4-(-1)=-7-(-4)= -3

Formula of sum of first n terms :

Put n =25

Hence the sum of first 25 terms of an AP  is -925

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