Question

the 14th term of an ap is twice its 8th term if it is 6th term is minus 8 then find the sum of the first 20 terms​

Answer 1

Answer:

Given 14th term of ap is twice 8th term

6th term is -8

sum of first nterms in ap

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

Step-by-step explanation:

1. a+13d=2a+14d
2. =>a=-d
3. so 6th term is -8
4. a+5d=-8
5. 4d=-8
6. d=-2
7. a=2
8. so sum offirst 20 terms
9. =20/2(2+19(-2))
10. = -360