vector{AB}=(4-9;-7-(-6))=(-5;-1)
vector{CD}=(x-2;-y-(-3))=(x-2;y+3)
|vector{AB}|=sqrt((-5)^2+(-1)^2)=sqrt(26)
|vector{CD}|=sqrt(104)=sqrt(4*26)=2sqrt(26)
vector{CD}=2*vector{AB}=
⇒
x-2=2*(-5)
y+3=2*(-1)
x=-8
y=-5
[b]D(-8;-5)[/b]