1,已知a,b,x,y满足a+b=x+y=2,ax+by=5,则(a^2+b^2)xy+ab(x^2+y^2)=?2,实数x,y,z满足x+y+z=5,xy+yz+xz=3,则z的最大值是?3,已知a,b是实数,关于x,y的方程组,y=x^3-ax^2-bx,y=ax+b 有整数解(x,y),求a,b满足的关系式.4,已知a0,且
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![1,已知a,b,x,y满足a+b=x+y=2,ax+by=5,则(a^2+b^2)xy+ab(x^2+y^2)=?2,实数x,y,z满足x+y+z=5,xy+yz+xz=3,则z的最大值是?3,已知a,b是实数,关于x,y的方程组,y=x^3-ax^2-bx,y=ax+b 有整数解(x,y),求a,b满足的关系式.4,已知a0,且](/uploads/image/z/1057092-60-2.jpg?t=1%2C%E5%B7%B2%E7%9F%A5a%2Cb%2Cx%2Cy%E6%BB%A1%E8%B6%B3a%2Bb%3Dx%2By%3D2%2Cax%2Bby%3D5%2C%E5%88%99%28a%5E2%2Bb%5E2%29xy%2Bab%28x%5E2%2By%5E2%29%3D%3F2%2C%E5%AE%9E%E6%95%B0x%2Cy%2Cz%E6%BB%A1%E8%B6%B3x%2By%2Bz%3D5%2Cxy%2Byz%2Bxz%3D3%2C%E5%88%99z%E7%9A%84%E6%9C%80%E5%A4%A7%E5%80%BC%E6%98%AF%3F3%2C%E5%B7%B2%E7%9F%A5a%2Cb%E6%98%AF%E5%AE%9E%E6%95%B0%2C%E5%85%B3%E4%BA%8Ex%2Cy%E7%9A%84%E6%96%B9%E7%A8%8B%E7%BB%84%2Cy%3Dx%5E3-ax%5E2-bx%2Cy%3Dax%2Bb+%E6%9C%89%E6%95%B4%E6%95%B0%E8%A7%A3%EF%BC%88x%2Cy%EF%BC%89%2C%E6%B1%82a%2Cb%E6%BB%A1%E8%B6%B3%E7%9A%84%E5%85%B3%E7%B3%BB%E5%BC%8F.4%2C%E5%B7%B2%E7%9F%A5a0%2C%E4%B8%94)
1,已知a,b,x,y满足a+b=x+y=2,ax+by=5,则(a^2+b^2)xy+ab(x^2+y^2)=?2,实数x,y,z满足x+y+z=5,xy+yz+xz=3,则z的最大值是?3,已知a,b是实数,关于x,y的方程组,y=x^3-ax^2-bx,y=ax+b 有整数解(x,y),求a,b满足的关系式.4,已知a0,且
1,已知a,b,x,y满足a+b=x+y=2,ax+by=5,则(a^2+b^2)xy+ab(x^2+y^2)=?
2,实数x,y,z满足x+y+z=5,xy+yz+xz=3,则z的最大值是?
3,已知a,b是实数,关于x,y的方程组,y=x^3-ax^2-bx,y=ax+b 有整数解(x,y),求a,b满足的关系式.
4,已知a0,且根号下(b^2-4ac)=b-2ac,求b^2-4ac得最小值
1,已知a,b,x,y满足a+b=x+y=2,ax+by=5,则(a^2+b^2)xy+ab(x^2+y^2)=?2,实数x,y,z满足x+y+z=5,xy+yz+xz=3,则z的最大值是?3,已知a,b是实数,关于x,y的方程组,y=x^3-ax^2-bx,y=ax+b 有整数解(x,y),求a,b满足的关系式.4,已知a0,且
2.实数x,y,z 满足 x+y+z=5,xy+yz+zx=3 ,则z的最大值是:13/3
∵xy+yz+zx=3,x+y+z=5
∴x+y=5-z
∴2xy=6-2(y+x)z=6-2(5-z)z=2z^2-10z+6
∴2*(xy+yz+zx)=6
∵x+y+z=5
∴(x+y+z)^2=25
x^2+y^2+z^2+2*(xy+xz+yz)=25
x^2+y^2+z^2=19
∵(x-y)^2≥0,
x^2+y^2-2xy≥0,
x^2+y^2≥2xy,
∴x^2+y^2=2xy时,z^2有最大值,
∴z^2+2xy=19,
∴z^2+2z^2-10z+6=19,
3z^2-10z-13=0
z^2-10z/3-13/3=0
(z-5/3)^2-(8/3)^2=0
(z-13/3)*(z+1)=0
z1=13/3
z2=-1
z1>z2
故z的最大值=13/3
答:实数x,y,z 满足 x+y+z=5,xy+yz+zx=3 ,则z的最大值是13/3