Question

Giúp mình câu 14,18,20 thôi nhé mình cảm ơn

Answer 1

14.

\(\overrightarrow{a}=\left(2;-3\right)\) ; \(\overrightarrow{b}=\left(1;2\right)\)

\(\Rightarrow\overrightarrow{a}-\overrightarrow{b}=\left(1;-5\right)\)

18.

\(\overrightarrow{a}=\overrightarrow{b}\Rightarrow\left\{{}\begin{matrix}m-2=3\\2n+1=-2\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}m=5\\n=-\dfrac{3}{2}\end{matrix}\right.\)

20.

\(\overrightarrow{MN}=\left(-4;2\right)\Rightarrow MN=\sqrt{\left(-4\right)^2+2^2}=2\sqrt{5}\)