Question

the 9th term of an AP is 449 and 449th term is 9.the term which is equal to zero is:-
(a)501th
(b)502th
(c)508th
(d)none of these​

Answer 1

Answer:

d) none of these

Step-by-step explanation:

an = a + (n-1)d

ATQ,

449 = a + (9-1)d

=> 449 = a + 8d (1)

And, 9 = a + (449-1)d

=> 9 = a + 448d (2)

(2) - (1)

=> 9-449 = a + 448d - (a + 8d)

=> -440 = 440d

=> d = -1

So, in (1)

=> 449 = a + 8×-1

=> 449 = a - 8

=> a = 449+8 = 457

Now, as asked in the question we have to find 'n' such that 'an' is 0 -

an = a + (n-1)d

=> 0 = 457 + (n-1) (-1)

=> -457 = 1 - n

=> n = 1+457 = 458

Hence, 458th term is 0

Here, 'n' is number of term

'an' is value of nth term

'a' is first term of A.P

'd' is common difference of A.P