用配方法说明xx+yy+x-y+1的值都为正数

用配方法说明xx+yy+x-y+1的值都为正数 已知2x=3y,求xy/xx+yy-yy/xx-yy的值 已知x（x+1)-(xx+y)=3,求(xx+yy)/2-xy的值 x(x+1)-(xx+y)=-3,求(xx+yy)/2-xy的值 xx+2x+yy+6y+10=0求xx+yy的值 已知xx+yy+4x-6y+13=0,求（xx-2x）/xx+3yy的值. 若xx+yy-2x-6y+10=0,求分式（xx-yy）/xy的值. xx-yy-x-y 因式分解 若xx-2x+yy+6y+10=0 求xx-yyy的值 若xx-2x+yy+6y+10=0 求xx-yyy的值 x-y=3,(x+y)(x+y)=25,求xy/xx+yy的值? 若xx+yy+2x+2y+1=0,则x+y的取值范围是? xx+yy+5/4 =2x+y 求x+y的值 (x-y)(x+y)(xx-yy)=? XX-YY/(X-Y)(X-Y)约分 已知(x+y)(x+y)=25,(x-y)(x-y)=9求xy与xx+yy的值 matlab怎么写约束条件：常值=x+yx=linspace(1,20,50);y=linspace(1,20,50);[xx,yy]= meshgrid (x,y);（xx+yy=常值）zz=2.*xx.*yy./(xx+yy);surf(xx,yy,zz) 初二数学因式分解已知x-y+1的绝对值与xx+8x+16互为相反数,求xx+2xy+yy的值