17)(1/2 x+1/3 y+1/4 z)(-1/3 x-1/2 y-1/4 z);

17) Раскроем скобки:

$$(\frac{1}{2}x + \frac{1}{3}y + \frac{1}{4}z)(-\frac{1}{3}x - \frac{1}{2}y - \frac{1}{4}z) = -\frac{1}{6}x^2 - \frac{1}{4}xy - \frac{1}{8}xz - \frac{1}{9}xy - \frac{1}{6}y^2 - \frac{1}{12}yz - \frac{1}{12}xz - \frac{1}{8}yz - \frac{1}{16}z^2 = -\frac{1}{6}x^2 - \frac{13}{36}xy - \frac{5}{24}xz - \frac{1}{6}y^2 - \frac{5}{24}yz - \frac{1}{16}z^2 $$.

Ответ: $$-\frac{1}{6}x^2 - \frac{13}{36}xy - \frac{5}{24}xz - \frac{1}{6}y^2 - \frac{5}{24}yz - \frac{1}{16}z^2$$