Question 33381
To solve this, use the FOIL method.  First, Outside, Inside, Last.

(y x y) (y x 1) (y x -1) (1 x -1) =

y^2 + 1y - 1y -1

Because you can cancel out the 1y and -1y you are left with Y^2 - 1 or Y squared -1.  Hope this helps.

Jonna