Question

if nth term of the ap 9,7,5 ...is same as the nth term of the ap 15 ,12 ,9, find n​

Answer 1

Answer :

• n = 7

Explanation :

Given that,

The nth term of A. P. :- 9, 7, 5 . . . . is same as the nth term of the A. P. :- 15, 12, 19. . . .

Find ‘n’

Here,

nth term of first A. P. is given by,

⇒ a + (n - 1) × d

Where,

• a(first term) = 9
• d(common difference) = -2

⇒ 9 + (n - 1)-2

⇒ 9 - 2n + 2

⇒ 11 - 2n

And also,

nth term of the second A. P. will be,

⇒ 15 + (n - 1)-3

⇒ 15 - 3n + 3

⇒ 18 - 3n

According to the question,

⇒ 18 - 3n = 11 - 2n

⇒ 18 - 11 = 3n - 2n

⇒ 7 = n

∴ Value of ‘n’ is 7