Have a repeat in about 8hrs so any help much appreciated.

Solve the initial value problem y"+y'-2y=0, y(0), y'(0)=1

For m1 I am getting -2 and for m2 I am getting 2.

These are different so I use the formula: y(x)=Ae^m1x+Be^m2x

But as far as I know if the numbers are the same I use a different formula and I think there is a third formula. I can't find these anywhere so if someone knows them or has a link I would really appreciate it.