# Math Help - finding a formula for a recurrence

1. ## finding a formula for a recurrence

Find a formula for $Tn$ if $Tn = 3Tn-2 + 5$, with initial conditions
$T0 = 1$ and $T1 = 2$.

I have $x^3-3x-5 = 0$ for my characteristics equation and I'm not sure if it's right or not. If it is right, how do I find the roots??

2. Originally Posted by sbankica
Find a formula for $Tn$ if $Tn = 3Tn-2 + 5$, with initial conditions
$T0 = 1$ and $T1 = 2$.

I have $x^3-3x-5 = 0$ for my characteristics equation and I'm not sure if it's right or not. If it is right, how do I find the roots??
Do you mean
$T_n = 3*T_{n-2} + 5$
Where
$T_0 = 1$ and $T_1 = 2$

3. what happens to the +5 though?? do you not consider it when finding the roots?