Question

ques no. 8th by Arthematic progression

Answer 1

$\bold{\boxed{HEY!!!}}$



$<B><I>HERE IS YOUR ANSWER :-$



$\underline{GIVEN}$



t1 = a = - 3



t2 = 4



$\underline{\:TO\:FIND}$



t21 = ?



$\underline{SOLUTION}$



- 3 , 4 , ... is an A.P.



d = t2 - t1


= 4 - ( - 3 )


= 4 + 3


= 7



$\bold{\boxed{d = 7}}$



We known that



tn = a + ( n - 1 )d



t21 = - 3 + ( 21 - 1 )7



= - 3 + 20 × 7



= - 3 + 140



= 137.



$\bold{\boxed{t21=137}}$

Answer 2

$\underline \bold {Solution:-}$

First term (a) = -3.

Second term = 4

Common difference (d) = Second term - First term

d = 4 - (-3)

d = 7

We have to find out the 21th term of A.P.

We know that,

$a_{n} = a + (n - 1)d$

On putting n = 21

$a_{21} = a + (21 - 1)d \\ \\ a_{21} =a + 20d \\ \\ a_{21} = - 3 + 20(7) \\ \\ a_{21} = - 3 + 140 \\ \\ a_{21} =137$

So, the 21th term of the A.P. is 137.