LordZpider:

#1 should have the y in the numerator rather than the denominator. Oh, and the other root is 0.

#2 is correct.

#3 is correct.

#4 is correct.

#5 is incorrect. You can't turn (x+y)/(x-y)=2xy into
-(y-x)/(x-y)=2xy, trying to break out -1 would result in -(-y-x)/(x-y)=2xy.

"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram