# Choose the correct answer from the given four options:The $21^{\text {st }}$ term of the AP whose first two terms are $-3$ and 4 is(A) 17(B) 137(C) 143(D) $-143$

#### Complete Python Prime Pack

9 Courses     2 eBooks

#### Artificial Intelligence & Machine Learning Prime Pack

6 Courses     1 eBooks

#### Java Prime Pack

9 Courses     2 eBooks

Given:

First two terms of the A.P. are $–3$ and $4$.

To do:

We have to find the $21^{st}$ term of the A.P.

Solution:

$-3,\ 4,\ 11,\ 18\ .......$

Here, first term $a=-3$

Common difference, $D=7$

$n=21$

Now, $A_n=a+( n-1)d$

$\Rightarrow a_{21}=-3+20\times( 7)$

$\Rightarrow a_{21}=-3+140$

$\Rightarrow a_{21}=137$

Hence the $21^{st}$ term of the A.P. is $137$.

Updated on 10-Oct-2022 13:27:27