x^2-y^2=[x+y][x-y]=18x-y=18/6=32x=9x=4.5y=6-4.5=1.5
x=6-y(6-y)^2-y^2=186^2-12y+Y^2-y^2=1836-18=12y18=12yy=1.5x=4.5(或y=2/3x=9/2)