Question

If a₁ = 9 and an= 4an-1 then find the value of a5.

Answer 1

Explanation:

an = 4an-1

means that

a2 = 4×a1

a3 = 4×a2 = 4×(4×a1)

so,

an = a1 × 4^(n-1) = 9 × 4^(n-1)

therefore,

a5 = 9 × 4⁴ = 9 × 256 = 2,304