Q1

Which term of A.P. 8, 14, 20, 26,… will be 72 more than its 41^st term?

Q2

Which term of the sequences 114,109,104 ………is the first negative term?

Q3

Find four terms is an A.P., whose sum is 20 and the sum of whose square is 120.

1 )

for such sums you need to first know the 41st term 

In this AP :

First term ( a ) = 8 

Common difference ( d ) = 6

Fourty- first term ( a41 ) = a + 40d

                                           = 8 + 40 ( 6 )

                                           =  248 .

now add 72 to this .

248 + 72 = 320

this number will be the an 

320 = a + ( n -1 ) d

        = 8 + ( n -1 ) 6

         = 8 + 6n -6

         = 2 + 6n

318  =  6n

n = 318 / 6

    = 53 . 

the 53rd term is 72 more than its 41st term .

@ PUSHKALA thnx a lot