已知x,y满足x≦3,3x+2y≥6,2y≥x,3y≦x+9,那么z=2x-y的最大值是

已知x,y满足约束条件 2x+5y>=10 2x-3y>=-6 2x+y 已知x,y满足约束条件{2x+5y>=10,2x-3y>=-6,2x+y 已知实数x,y满足2x+5y>=10;2x-3y>-6;2x+y 已知x,y满足x≦3,3x+2y≥6,2y≥x,3y≦x+9,那么z=2x-y的最大值是 已知X和Y满足3X+4Y=2,X-Y-1/7 已知x和y满足3x+4y=2,x-y 已知实数x,y满足,X-2y≥-4,3x-2y≤12,x+y≥2,则y/(x+1)的取值范围 化简求值：已知x、y满足：x^2+y^2-4x+6y+13=0 求代数式 的值.(3x+y)^2-3(3x-y)(x+y)-(x-3y)(x+3y)急用！ 已知x.y满足(x-y-2≤0,x 2y-5≥0,y-2≤0 则3x+y/x+1得多少 已知实数x,y满足条件x≥0,y≥x,3x+4y≤12,则(x+2y+3)/(x +1)的最大值是 已知x和y满足x＋3y＋|3x－y|＝19,2x＋y＝6,求x,y的值 已知x、y满足1/2x＞1,-2x≥-8和y-1＞-1,3y≤6,比较X、Y的大小 已知x=3y+2,且满足4y 已知x=3y+2,且满足4y 已知实数x.y满足根号(x+y-8)+根号(8-x-y)=根号(3x-y-4)+根号(x-2y+7),求x,y 已知X,Y满足|X-Y-1|+（X+Y-3)^2=0求X,Y的值 已知x,y满足x+y-6≤0,x+2y-8≤0,2x-3y-6≤0,x≥0,0≤y≤3,求(3y-12)/(x-6)的最大值和最小值. 已知x、y满足x2+y2-4x+6y+13=0 求代数式（3x+y)2-3(3x-y)(x+y)-(x-3y)(x+3y)已知x、y满足x^2+y^2-4x+6y+13=0 求代数式（3x+y)^2-3(3x-y)(x+y)-(x-3y)(x+3y)的值