Question

In an Ap an=4, d=2 s=-14 find n and a

Answer 1

Answer:

n=7,a=-8

Step-by-step explanation:

an=a+(n-1)d

4=a+2n-2

a=6-2n------1

s=n/2{2a+(n-1)d}

-14=n/2(12-4n+2n-2). putting value of a from 1

-28=n(-2n+10)

-28=-2n^2+10n

2n^2-10n-28=0

n^2-5n-14=0

n=7

put n in eqn 1

a=-8