Question

In an A.P. if the 12th term is -13 and the sum of its first four terms is 24. Find
the sum of its first 20 terms.

see the points you will get for relevant answers..plz gve relevent answers but plz answer this urgent​

Answer 1

Answer:

Step-by-step explanation:

Given:

$t_{12} =-13$ We know that $t_{n} =a+(n-1)d$

$a+11d=-13$----------------------- 1

$s_{4}= 24$ we know that $s_{n} = n/2[2a+(n-1)d]$

$4/2[2a+3d]=24$

$2a+3d=12-----------------2$

solving 1 and 2

d=-2 a=9

Sum of first 20 terms

$s_{20} =20/2[2(9)+19(-2)]\\ =10[18-38]\\ =10[-20]\\ = -200$

Answer 2

Here is your answer......