Help with recurrence relation It 's been a long time since I touched this kind of math , so please help me to solve the relation step by steps : 
$V_k = (1+i)*V_{k-1}+P$ 
I know the answer is  $V_k = (P/i)*((1+i)^k-1) $ 
Thanks in advance.

Yet another way is:
$V_k - r V_{k-1} = P$
$r V_{k-1} - r^2 V_{k-2} = P r$
...
$V_k - r^n V_0 = P ( 1 + r + ... + r^{n-1} ) = P\frac{1-r^n}{1-r}$
(The last equality is only valid when $r \ne 1$, otherwise it should be $Pn$)
And one more:
(This method works only if $r \ne 1$, but the idea can be applied to other recurrences.)
$V_k - \frac{P}{1-r} = r ( V_{k-1} - \frac{P}{1-r} ) = r^n ( V_0 - \frac{P}{1-r} )$
(The constant that dropped from the sky was found by putting it in and solving for it.)
