5x²-3(y+1) (y-1)

5x²-3(y+1) (y-1)=5x²-3(y²-1)=5x²-3y²+3   ze wzoru skr mnoz   (a-b)(a+b)=a²-b² (y+1) (y-1)=y²-1

5x²-3(y+1) (y-1) = 5x²-3(y²-1²) = 5x²-3(y²-1)=5x²-3y²+3