Question

If a1= 4 and an = 5an-1 -4 then find the value of a3

Answer 1

we need to solve in order

`a_1=4`
`\begin{gathered} a_2=5a_(2-1)-4 \\ a_2=5a_1-4 \\ a_2=5(4)-4 \\ a_2=20-4 \\ a_2=16 \end{gathered}`
`\begin{gathered} a_3=5a_(3-1)-4 \\ a_3=5a_2-4 \\ a_3=5(16)-4 \\ a_3=80-4 \\ a_3=76 \end{gathered}`

the value of a3 is 76