Question

Find an expression for the nth term ( tn ) in each of the following sequences:

t2 = 9; t4 = 25

Answer 1

The expression for the nth term is Tn = 8n -7

Explanation:

Here, we are to find an expression for the nth term of the sequence.

Mathematically, the nth term of an arithmetic sequence can be expressed as;

Tn = a + (n-1)d

for T2, the equation is

a + d = 9

for T4, the equation is

a + 3d = 25

we can substitute the equation of T2 into T4 but we first need to rewrite T4

a + d + 2d = 25

9 + 2d = 25

2d = 25 -9

2d = 16

d = 16/2

d = 8

now since a + d = 9

a = 9-d

a = 9-8

a = 1

So the expression for the nth term would be;

1 + (n-1)8

1 + 8n - 8

= 8n -8+1

= 8n -7