I have the following problem to solve:
a_n = 4a_{n-1} - 4a_{n-2}
where a_0 = -5 and a_1 = 3
which I have attempted to solve via substitution, ie a_n = r^n
When I do this, I end up with the result (r-2)^2 = 0
hence, r = 2.
When I put this back into the equation, I then get
A + B = -5
2A + 2B = 2(A + B) = 3
=> 0 = 13.
What am I fumbling in here??