Question

In an AP the sum of first ten terms is -80 and the sum of next 10 terms is -280. Find the AP

Answer 1

now you can apply simultaneous equation on equation one and two

Answer 2

Answer:

Step-by-step explanation:

S10=-80

S10=5[2a+(10-1)d]

-80=5[2a+9d]

-16=2a+9d

S10+10=-280

S20=10[2a+19d]

-280=10[2a+19d]

-28=2a+A19d

2a+19d=-28

2a+9d=-16

- +

10d=-12

d=-6/5

Substitute d in the following,

2a+9d=-16

2a+9x-6/5=-16

a =-13/5

A.P.=-13/5,-19/5,-5,-31/5,……………

I hope my answer can help you