what the answer?

Question

Write a formula for the general term (the nth term) of the arithmetic sequence. Then use the formula for a_n to find a₂₀, the 20th term of the sequence.

a₁ = 2, d = -0.3

which one?:

a_n = 2n - 0.3; a₂₀ = 39.7

a_n = 2n - 2.3; a₂₀ = 37.7

a_n = -0.3n + 2.3; a₂₀ = -3.7

a_n = -0.3n + 2; a₂₀ = -4

Answer 1

a_n = a₁ + (n - 1)d

a₂₀ = a₁ + (19)d

a₂₀ = 2 + (19)(-0.3)

a₂₀ = 2 - 5.7

a₂₀ = -3.7

Fourth equation has the correct value, yet it is missing -1 after the n.