The values of the first and last terms are given. How many terms are there in the arithmetic sequence?
- 7, - 2, 3
Practice makes perfect
We want to find the arithmetic means in the given arithmetic sequence. To do so, we first have to find the value of the common difference d.
-12, , , , 8
We see that the first term is a_1= - 12 and there are 5 total terms. Therefore, we have that n= 5. We can substitute these two values in the general formula for the nth term of an arithmetic sequence.
a_n= a_1+( n-1)d ⇓ a_5= - 12+( 5-1)d
We are also given the value of the last term, 8. Since n=5, we have that a_5=8. Let's substitute this into our formula and solve for d.
