Question

A student uses the explicit formula an= 5+3(n-1) for the sequence 3,8,13,18,23,...to find the 12th term. Explain the error the student made.

Answer 1

Answer:

Formula should be an =  3 + 5(n - 1)

The 12th term = 3 + 5(12 - 1) = 58

Step-by-step explanation:

Let's find the value of the first term using the given formula:-

n = 1 is plugged into the formula:-

a1 = 5 + 3(1- 1)

= 5 + 3(0)

= 5  

This gives the wrong value ( it is 3)  so the formula is incorrect.

If we study the sequence we see that the common difference is  8-3  = 13 - 8 = 5 and the first term is 3.

The student has confused the first term with the common difference

The correct formula is an = 3 + 5(n - 1)