x^2+y^2=6x-4y-9,则2x-3y的最小值和最大值的和,把最大值和最小值是什么写明白

来源：学生作业帮助网编辑：作业帮时间：2024/04/29 18:23:31

x^2+y^2=6x-4y-9,则2x-3y的最小值和最大值的和,把最大值和最小值是什么写明白
x^2+y^2=6x-4y-9,则2x-3y的最小值和最大值的和,把最大值和最小值是什么写明白

x^2+y^2=6x-4y-9,则2x-3y的最小值和最大值的和,把最大值和最小值是什么写明白
x^2+y^2=6x-4y-9
x^2+y^2-6x+4y+9=0
(x-3)^2+(y+2)^2=4
(x-3)^2=0 y=-4 x=3 (2x-3y)max=2*3-3*(-4)=18
y=0 x=3 (2x-3y)min=6
(y+2)^2=0 x=5 y=-2 (2x-3y)=16
x=1 y=-2 (2x-3y)=8
min+max=24

变形为（x-3）^2+(y+2)^2=2^2则用参数方程x=3+2cosa y=-2+2sina 2x-3y=2(3+2cosa )-3(-2+2sina)=12+4cosa-6sina=12+(4^2+6^2)^0.5sinb=12+2(13)^0.5sinb
所以最大值为12+2(13)^0.5，最小值为12-2(13)^0.5，和为24.

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 81/8*(-x-y)^6*(x-y)^3*4/9(x+y)^4*(y-x)^2 （x+y）/2- x-y/2=6 3(x+y)=4(x-y) x+y/3+x-y/2=6 4(x+y)-2(x-y)=40 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 【2(x-y)(x-y)(x-y)-8(x-y)(x-y)(x+y)+6y(x-y)(x-y)]/2(x-y)(x-y) 若2x^2-6xy+9y^2-4x+4=0,则y/x-x/y=若2x^2-6xy+9y^2-4x+4=0,则y/x-x/y=? 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 已知x,y为实数,根号3x+4 +y^2-6Y+9=0则x+y=? (x+y)^2+6(x+y)+9