Question

Please HELP! MEDAL!
Which of the following is the explicit formula for the sequence below?

3, 11, 19, 27, ...
A. an = 3 + 8(n - 1)
B. an = 8 + 3n
C. an = 3 + 8n
D. an = 8 + 3(n - 1)

Answer 1

first recal the formula for arithmetic sequences:
an = a1 + (n-1)*d
can u identify what 'd' is? it is the difference from one number to the next.

Answer 2

:/ :/ :/ Identify D? What do you mean

Answer 3

'd' is the difference between each number in the sequence of 3, 11, 19, 27

Answer 4

2, -8, -8

Answer 5

yep, you get the idea, but the method is like this:
d = 11-3 or
d = 19-11

so we get positive 8 as 'd'

next is to identify a1 of the formula i posted earlier. a1 represents the first number in the sequence, which is..?

Answer 6

3

Answer 7

correct

so,
d = 8 and
a1 = 3

substitute those into the formula:
an = a1 + (n-1)d