How to simplify these ->

These problems confuse me completely. Simplify ->

1/1-x + x/x-1

x/1-x^2 - x/1-x

6x-18/x^2-16 • x^2+5x+6/x^2-9


(• = multiplying) Anyone to help gets Best Answer :}Thanks.

1)

You can see that 1 - x = - (x - 1)

1/(1-x) + x/(x-1) =

1/(1 - x) - x/(1 - x) =

(1 - x)/(1 - x) = 1

2)

x/(1 - x^2) - x/(1 - x)

(x - x*(1 + x))/(1 - x^2) = - (x^2)/(1 - x^2) = (x^2)/(x^2 - 1)

3)

(6*(x - 3)/(x + 4)*(x - 4) )*(x + 3)*(x + 2)/(x + 3)*(x - 3) = 6*(x + 2)/(x^2 - 16)