Question

In an ap if the 12th term is -13. and the sum of first four term is 24. what is the sum of the first 10th term formula

Answer 1

12th term = -13

a+11 d= -13  ---------------(i)

Now,

$S_{4} = \frac{4}{2} (2a + 3d) =24$

 now,

2 (2a + 3d) = 24

=>2a+3d = 12------------------(ii)

Multiplying 2 in equation (i) and subtracting with equation (ii),

we get d = -2

Putting the value of "d" in eq (i)
we get a = 9

Now ,$S_{10} = 0$