[tex]\frac{1}{2}x+3y-\frac{3}{4}x-4y+\frac{1}{2}y-5=\frac{2}{4}x-\frac{3}{4}x-y+\frac{1}{2}y-5=-\frac{1}{4}x-\frac{1}{2}y-5[/tex]
[tex]2x^2-4y-3x^2-5y+5xy-6=-x^2-9y+5xy-6[/tex]
