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Determinat m E R ai punctele A(3,3) B(2,4) C(2m,1-m) sa fie coliniare. 
Plzzz 


Răspuns :

A,B,C coliniare <=> xAyB-xByA+xByC-xCyB+xCyA-xAyC=0 => 3*4-3*2+2*(1-m)-8m+6m-3(1-m)=0 => 12-6+2m-2-8m+6m-3+3m=0 => 3m+1=0 => m=-1/3
  sau mai poti calcula cu [tex]det \left[\begin{array}{ccc}xA&yA&1\\xB&yB&1\\xC&yC&1\end{array}\right] =0[/tex]