`A(3;2) ; B(-5;1)`
`a)V_{(O,2)} (A)=C<=>\vec{OC}=2\vec{OA}`
`<=>(x_C;y_C)=2(3;2)=(6;4)`
`=>C(6;4)`
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`b)V_{(O,3)} (B)=D<=>\vec{OD}=3\vec{OB}`
`<=>(x_D;y_D)=3(-5;1)=(-15;3)`
`=>D(-15;3)`
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`c)V_{(O, 1/2)} (E)=A<=>\vec{OA}=1/2\vec{OE}`
`<=>\vec{OE}=2\vec{OA}`
`<=>(x_E;y_E)=2(3;2)=(6;4)`
`=>E(6;4)`
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`d)V_{(A,3)} (B)=F<=>\vec{AF}=3\vec{AB}`
`<=>(x_F-3;y_F-2)=3(-8;-1)<=>{(x_F-3=-24),(y_F-2=-3):}<=>{(x_F=-21),(y_F=-1):}`
`=>F(-21;-1)`