1.

The range of `x^2+4y^2+9z^2-6yz-3xz-2xy` is

Answer» `f=x^2+4y^2+9z^2-6yz-3xz-2xy`
`f=x^2+(2y)^2+(3z)^2-(2y)(3z)-(x)(3z)-(2y)(x)`
`f=1/2*(2a^2+2b^2+2c^2-2ab-2bc-2ca)`
`f=1/2{(x-2y)^2+(2y-3z)^2+(x-3z)^2}`
`f>=0`
`f[0,oo)`.


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