Question

What is the nth term of the arithmetic sequence 7,5,3,1?

Answer 1

tn = 7 + (n - 1)*(-2) or

tn = 9 - 2n

Explanation:

You are (beginning with 7) subtracting 2 from the term to the left.

a = 7

d = -2

tn = a1 + (n - 1)*d

tn = 7 + (n - 1)*(-2)

Try this out on n = 4

t4 = 7 + (4 - 1)*-2

t4 = 7 + (3) (-2)

t4 = 7 - 6

t4 = 1 just as it says.

More generally

tn = 7 + (n - 1)*-2

tn = 7 + (-2n) + 2

tn = 9 - 2n