Question

Find the next two terms in the given sequence, then write it in recursive form. A.) {7,12,17,22,27,...} B.) { 3,7,15,31,63,...}​

Answer 1

Answer:

A) a_n = 5n + 2

B) a_n = (2^(n + 1)) - 1

Step-by-step explanation:

A) The sequence is given as;

{7,12,17,22,27,...}

The differences are:

5,5,5,5.

This is an arithmetic sequence following the formula;

a_n = a_1 + (n - 1)d

d is 5

Thus;

a_n = a_1 + (n - 1)5

Now, a_1 = 7. Thus;

a_n = 7 + 5n - 5

a_n = 5n + 2

B) The sequence is given as;

{ 3,7,15,31,63,...}​

Now, let's write out the differences of this sequence:

Differences are:

4, 8, 16, 32

This shows that it is a geometric sequence with a common ratio of 2.

In the given sequence, a_1 = 3 and a_2 = 7 and a_3 = 15

Thus, a_2 = 2a_1 + 1

Also, a_(2 + 1) = 2a_2 + 1

Combining both equations, we can deduce that: a_(n + 1) = 2a_n + 1

Thus; a_n can be expressed as:

a_n = (2^(n + 1)) - 1