Question

Will someone like please help me on my math ;(

What is the recursive formula for this sequence?
10, 14, 18, 22, 26....?!!?!

Answer 1

option A

Explanation:

The given Series:

10,14,18,22,26... is an Arithmetic Progression.

Concept:

The difference between consecutive numbers always remains the same.

For instance:

14 - 10 = 18 - 14 = 22 - 18 = 4

This difference is known as the common difference.

In an A.P., the nth (an) term of a series can be found out by:

`\boxed{ \sf{a _(n) = a + (n - 1)d}}`

Here,

• an is the nth term
• a is the first term of the series = 10
• n is the number of terms
• d is the common difference = 4

[Don't get confused by (n- 1), it's simply the number of terms - 1. If the number of terms, somehow, is (n - 1) itself, your formula will be an = a + ((n - 1) -1)d]

Soltution:

The first term of the given Series is 10.

==> a1 = 10

Finding an:

the nth term will be:

an = 10 + (n - 1)4

==> 10 + 4n - 4

==> 6 + 4n

Strategy:

All the given options have an and a(n-1). So we have to deduce a relation between an and a(n- 1).

Finding a(n-1):

==> a(n-1) = 10 + ((n - 1) -1)4

= 10 + (n- 2)4

= 10 + 4n - 8

= 4n + 2

Subtracting a(n-1) from an:

==> an - a(n-1) = 6 + 4n - (4n + 2)

==> an - a(n-1) = 6 + 4n - 4n - 2

==> an - a(n-1) = 4

==> an = 4 + a(n-1)

Hence, option A is the answer.