Question

The 10th term of an A.P -27 and the 5th term is -12. What is the sum of it's 25th term

Answer 1

Answer:

Hope it helps!!!

Answer 2

Answer:

Step-by-step explanation:

Let the first term be a and common difference be d

According to question

a+(10-1)d=-27

a+9d=-27.

a=-27-9d. -----------------(1)

a+(5-1)d=-12

a+4d=-12. ---------------(2)

Using (1) in (2)

-27-9d+4d=-12

-27-5d=-12

-5d=-12+27

-5d=15

d=-3

a=-27-9(-3)=-27+27=0

Sum of 25 terms = 25/2[2(0)+(25-1)-3]

=25/2[0+(24)-3]

=25/2[-72]

=-900