Question

What is the explicit formula for this sequence?
-7, -3, 1, 5, ...

Answer 1

Explanation:

a1 = - 7

d = 4

an = a1 + (n - 1) * d

an = - 7 + (n - 1) * 4

an = - 7 + 4n - 4

an = -11 + 4n

Try this out. Let n = 3

a3 = -11 + 4*3

a3 = - 11 + 12

a3 = 1 Which is what the series says.