Question

What is the sum of the first 11 terms of an arithmetic progression if the fourth term is the 11 and the 7 term is -4

Answer 1

HEY HERE IS YOUR ANSWER...

given,
a4= 11
a7= -4
s11 = ?

solution:
a + 3d = 11 -(1)
a + 6d = -4 -(2)

sub1 and 2 we get,
-3d = 15
d = 5
NOW, a = -4

s11 = 11/2 (-8 +50)
= 11 (21)
s 11 = 231.


HOPE THIS WOULD BE HELPFUL TO YOU...