Sagot :
NB(xB-xN; yB-yN) NC(xC-xN; yC-yN) NA(xA-xN; yA-yN)
X NB-XNC=XNA YNB-YNC=YNA
<=> xB-xN - [xC-xN]=xA-xN <=> yB-yN - [yC-yN]=yA-yN
<=> -4-xN-7+xN= 2-xN <=> 3-yN-5+xN = -1-yN
<=> -11=2-xN <=> -2=-1-yN
<=> -13=-xN <=>-1=-yN
<=> xN=13 <=> yN= 1
Soit N(13;1)