Question

Срочно, 30 баллов!!!!

Answer 1

$x^2m-x^2n-y^2m+z^2n+y^2n-mz^2=\\=(-x^2n+x^2m)+(y^2n-y^2m)+(z^2n-mz^2)= \\ =-x^2(n-m)+y^2(n-m)+z^2(n-m)=(n-m)(y^2+z^2-x^2)$

при 

$x=y=z=7; m=2 frac{1}{5}; n=-1 frac{4}{5} \ \ (n-m)(y^2+z^2-x^2)=(-1 frac{4}{5}-2 frac{1}{5} )(7^2+7^2-7^2)= \\ =(- frac{9}{5}- frac{11}{5} )*7^2=- frac{20}{5}*49=-4*49= -196$