if a1 = 7 and an = an-1 + 4 then find the value of a4

Answer 1

the arithmetic sequence has a common difference = d = 4 an- an-1 = 4

a4 = 3d + a1 = 3(4) + 7 = 12+7 = 19

an = (n-1)d + a1

IF you had wanted a23,

a23 = 22(4) +7 = 88+7 = 95

Answer 2

In order to solve, replace the value of the previous answer into the equation for the next answer.

a₁ = 7

a₂ = 7 + 4 = 11

a₃ = 11 + 4 = 15

a₄ = 15 + 4 = 19

Therefore, a₄ = 19