Sequences And Series Question (1 Viewer)

[Champagne Supernova]

The AP T4,T6,T8=-6
Find T6.
i started by
a+3d+a+5d+a+7d=-6
3a+15d=-6
then i got stuck, i might be approaching it wrong though
any help is appreciated, thanks.

 

[michael3]

The series T4 + T6 + T8 = -6 is:
a + (a+d) + (a+2d) = -6
So 3a + 3d = -6
Divide by 3:
a+d = -2 and since a+d = T6, T6 = -2

 

[Champagne Supernova]

Thanks, i see what i did wrong.