Question

in an arithmetic progression 2,7,12,17......summation of how many terms will be 990​

Answer 1

mark as brilliant answer

Answer 2

A.P : 2,7,12,17.............

a = 2 d = 7-2 = 5

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

990= n/2 [ 2(2) + (n-1) 5]

1980 = n [ 4+5n-5 ]

1980 = 5n2 - n

5n2-n-1980 = 0

by factorising it you will get 2 values for n

the value which is negative should be ignored.

HOPE IT HELPS..................