Question

Решите, пожалуйста !!!!

Answer 1

$1)\; \overline {a}=(2,-1,4)\; ,\; \; \overline {b}=(-3,1,-2)\\\\2)\; |\overline {a}|=\sqrt{4+1+16}=\sqrt{21}\; ,\; |\overline {b}|=\sqrt{9+1+4}=\sqrt{14}\\\\3)\; \overline {a}\cdot \overline {b}=-6-1-8=-15\\\\4)\; cos \alpha =\frac{-15}{\sqrt{21}\cdot \sqrt{14}}=-\frac{15}{7\sqrt6},\; \alpha =\pi -arccos\frac{15}{7\sqrt6}\\\\5)\; \overline {p}=(6,-3,12)-(-15,5,-10)=(21,-8,22)\\\\6)\; |\overline {p}|=\sqrt{21^2+8^2+22^2}=\sqrt{989}$