Question

the first term of an a.p is 7. the sum of the first 4 terms of the a.p is twice the sum of the next 4 terms. find the sum of the first 3o terms​

Answer 1

Answer:

Step-by-step explanation:

a=7

S4=n/2(2a+(n-1)d)

2(14+3d)

S8=n/2(2a+(n-1)d)

4(14+7d)

According to question

2(14+3d)=2(4(14+7d)

28+6d=2(56+28d)

28+6d=112+56d

-84=50d

d= -2

S30=15(14+29×-2)

S=660