18. Given points $A(3 ; 2), B(-1 ; 5), C(0 ; 3)$. Find the coordinates of the vectors $\overrightarrow{A B}, \overrightarrow{B C}, \overrightarrow{A C}$.
Solution. To find the coordinates of a vector, we subtract the coordinates of the beginning from the coordinates of the end. Then we get: $\overrightarrow{A B}=(-1-3$; $5-2)=(-4 ; 3) ; \overrightarrow{B C}=(0-(-1) ; 3-5)=(1 ;-2) ; \overrightarrow{A C}=(0-3 ; 3-2)=$ $=(-3 ; 1)$.