Question

What is a 15 of the sequence -7, 2, 11, ...? A. 128 B. 110 C. 136 D. 119

Answer 1

Answer:

D. 119

Step-by-step explanation:

To find the common difference, we take the second term and subtract the first term

2-(-7) = 9

We check  by taking the third term and subtracting the second

11-2 = 9

The common difference is 9

The formula for an arithmetic sequence is

an = a1 +d(n-1)

where a1 is the first term, d is the common difference and n is the number of the term in the sequence

a1=-7, d=9 and we are looking for the 15th term  so n=15

a15 = -7 +9(15-1)

a15 = -7+9(14)

      =-7 +126

      = 119