Question

Which term of the AP   21, 42, 63, 84,.....   is 252.​

Answer 1

Answer:

$n = 12$

Step-by-step explanation:

$a = 21 \: \: \: d = 42 - 21 = 21$

$an = a + (n - 1)d$

$252 = 21 + (n - 1)21$

$252 - 21 = (n - 1)21$

$\frac{231}{21} = n - 1$

$11 = n - 1$

$n = 11 + 1$

$n = 12$

i hope it will help u✌✌

Answer 2

Answer:

Follow the steps (solve by me only )

Step-by-step explanation:

In the given AP,

first term, a = 21

and

common difference, d = (42-21 ) = 21

Let its nth term be 0.

Then, Tn = 0  

⇒ a + (n - 1)d = 210

⇒ 21 + (n - 1) ⨯ (21) =210

⇒ 21 + 21n -1  = 210

⇒  20 + 21n = 210

⇒ 21n = 210 - 20

=21n = 190

n= 190/ 21