18 Given: the sequence 4, 7, 10, 13,... When using the arithmetic sequence formula a = a₁ + (n − 1)d
to determine the 10th term, which variable would be replaced with
the number 3?
(1) a₁
(2) n
(3) an
(4) d

a₁ = 4

n = 10

d = 3

a = a₁ + (n - 1)d

a₁₀ = 4 + (10 - 1)3

a₁₀ = 4 + (9)3

a₁₀ = 4 + 27

a₁₀ = 31

The 10th term would be 31 and the d variable will be replaced with the number 3.

the mistake in the pattern is that :

b. the decimal point was moved one too many place values each time

the correct pattern could be made by :

b. moving the decimal point to the right the same numbers of place values as the exponents