Question

Find the sum of the arithmetic series↓↓↓

Answer 1

\[d=-4,a _{n}=2,n=9\]

Answer 2

@acxbox22 @Hero

Answer 3

use formula
Sn=n/2 (2a+(n-1)xd)

Answer 4

How do i find \[a_{1}\]

Answer 5

use formula an=a+(n-1)xd

Answer 6

Use sigma to sum the sequence:

\[\sum_{k=0}^{n-1}(a+kd)=\frac{ n }{ 2}(2a+(n-1)d)\]

Answer 7

got it never mind i was dividing when i should have been subtracting...