A1 = 9 × 1 - 6 = 3
A2 = 18 - 6 = 12
A3 = 27 - 6 = 21
A4 = 36 - 6 = 30.
Explanation:
Σ ( 9n - 6 ) , n = 1
An = general term.
let Σ (An) = Σ (9n-6)
An = 9n-6
to determine the terms, plug in the value of n into the general term(An)
If you're asked for the 1st term then n = 1
if you're asked for the 2nd term then n = 2. and so forth.
To find the 1st 4 terms, just plug in 1 up to 4 into n bit by bit.
An = 9n - 6
A1 = 9 × 1 - 6 = 3
A2 = 18 - 6 = 12
A3 = 27 - 6 = 21
A4 = 36 - 6 = 30. done.
write the terms from 1 to 4 like this :
{ A1, A2, A3, A4 } = { 3, 12, 21, 30 }.