搜搜考试网已知y≠0且3x²-2xy-8y²=0求
来源：学生作业帮助网 编辑：作业帮 时间：2024/07/31 08:38:58
3x^2－2xy－8y^2＝0,（3x+4y)(x-2y)=03x+4y=0,或,x-2y=03x=-4y,或,x=2yx/y=-4/3,或,x/y=2
3x^2－2xy－8y^2＝0,（3x+4y)(x-2y)=03x+4y=0,或,x-2y=03x=-4y,或,x=2yx/y=-4/3,或,x/y=2
3x2-2xy-8y2=(3x+4y)(x-2y)=0so3x+4y=0orx-2y=0x/y=-4/3or2
3x²-2xy-8y²=0两边同除y²得:3(x/y)²-2(x/y)-8=0(3x/y+4)(x/y-2)=0x/y=2或x/y=-4/3
两边同除以xy,得3*(x/y)-2-8*(y/x)=0设x/y=a,则3a-2-8/a=0两边同时乘以a,得3a^2-2a-8=0(3a+4)*(a-2)=0∴a=2或-4/3即x/y=2或-4/3
因为xy不为0,所以3x^2-2xy-8y^2=0可以两边同时除以y^2,得3(x/y)^2-2(x/y)-8=0即(3x/y+4)(x/y-2)=0解得x/y=2或者x/y=-4/3希望有用.
答：x-7y=0x=7y≠0所以：x/y=7,y/x=1/7(x²-3xy+y²)/(2x²﹢xy-3y²)=(x/y-3+y/x)/(2x/y+1-3y/x)
∵x-y=6,xy=4∴(x-y)²=36∴x²-2xy+y²=36∴x²+y²=36+2×4=44两边除以xyx/y+y/x=44/4=11∴xy^
3x²-2xy-8y²=0(x-2y)(3x+4y)=0x=2y或3x=-4yx/y=2或x/y=-4/3
3x²-2xy-8y²=0(x-2y)(3x+4y)=0x=2y或x=-4y/3x/y+y/x=2+1/2=2.5或x/y+y/x=-4/3-3/4=-25/12
xy≠0,所以x≠0,y≠03x²-2xy-8y²=0两边除于xy3（x/y）-2-8（y/x）=0设x/y=t;t≠03t-8/t-2=03t²-2t-8=0(t-2)
填：3x+2y-2xy=02y+3x=2xy(2y+3x)/(2xy)=1(1/x)+(3/y)=1根据均值不等式得1≥2√(3/(xy))1≥12/(xy)xy≥12所以xy的最小值是12
2分之1或负4分之3
3x^2-2xy-8y^2=(3x+4y)(x-2y)=03x+4y=0,x/y=-4/3或x-2y=0,x/y=2
2X^2+3xy-2y^2=0(2x-y)(x+2y)=0即：2x-y=0或,x+2y=0y=2x或x=-2y当y=2x时：x+y/x-y=3x/(-x)=-3当x=-2y时：x+y/x-y=-y/(
∵x-y=4xy∴原式=[2(x-y)+3xy]/[-(x-y)-2xy]=(8xy+3xy)/(-4xy-2xy)=11xy/(-6xy)=-11/6
3x^2-2xy-8y^2=0(x-2y)(3x+4y)=01)x=2yx/y=22)3x=-4yx/y=-4/3