Question

The sum of first term and second terms of an A.P is 11 and sum of sixth and seventh terms is 41 find A.P?

Answer 1

a+ (a+d) = 11
2a+ d = 11
Also, (a+5d) +(a+6d) = 41
2a + 11d = 41
Solving these ..
a = -1 & d = 3
A.P = -1,2,5....

Answer 2

Sum of first term + second term = 11
a1 + a1 + d = 11
2a1 + d = 11...... (i)

sum of 6th and 7th = 41
a1+5d + a1+6d = 41
2a1 + 11d = 41....(ii)
(ii) - (i)
10d = 30
d = 3
(i)== 2a1 + d =11
2a1 + 3 =11
2a1 = 8
a1 =4
Hence A.P== 4, 7 , 10, 13, 16, 19, 22....