Question

Priyanka and Ethan were asked to find an explicit formula for the sequence -3,-14,-25,-36,...−3,−14,−25,−36,...minus, 3, comma, minus, 14, comma, minus, 25, comma, minus, 36, comma, point, point, point
Priyanka said the formula is g(n)=-3-11ng(n)=−3−11ng, left parenthesis, n, right parenthesis, equals, minus, 3, minus, 11, n.

Ethan said the formula is g(n)=-3+11ng(n)=−3+11ng, left parenthesis, n, right parenthesis, equals, minus, 3, plus, 11, n.

Which one of them is right?

Answer 1

Answer:

  neither one is right

Step-by-step explanation:

The sequence -3, -14, -25, -36, ... has a first term of -3 and a common difference of -11. The general term of such an arithmetic sequence is ...

  g(n) = g(1) +d(n -1)

where g(1) is the first term and d is the common difference. Putting our values into this equation gives us ...

  g(n) = -3 +(-11)(n -1)

  g(n) = 8 -11n . . . . . . . matches neither Priyanka's nor Ethan's result

_____

Please discuss this with your teacher. You should not have to put up with questions that have erroneous answer choices.

(Priyanka's is the closest wrong answer. It has the sign of the difference correct.)