Question

The number of terms common to the two A.P. 's 3, 7, 11, ....., 407 and 2, 9, 16, ....., 709 is ______.

Answer 1

3, 7, 11, ............ 407 d = 4 2, 9, 16 ............ 709 d = 7

1^st term commom of both series = 23

c.d = 28

407 = 23 + (n – 1)28

384/28 + 1 = n

n = 14.

Answer 2

Common term are : 23, 51, 79, ...... T_n