Hello,

I have a small algebra problem that i hope anyone can help me with. I have this example in my textbook that have this step i don't follow.

y_n-y_(n-1)-2y_(n-2) = 0 where n = 3,4,5,...

y_1 = 1

y_2 = 3

with y_n = x^n

x^n-x^(n-1)-2x^(n-2)=0

And what i don't understand is how they get this that to this:

x^2-x-2=0