a) a,b,c coliniare daca b∈ac
ecuatia dreptei ac : [tex] \frac{x-xa}{xc-xa} = \frac{y-ya}{yc-ya} [/tex]
<=> [tex] \frac{x-2}{1-2} = \frac{y-0}{6-0} [/tex] <=> 6x-12=-y /(-1) <=> 12-6x=y
Pentru ca b sa apartina ac => f(0)=4
f(0)=12 => b∉ac => a,b,c nu sunt coliniare.
b) A=1/2*|Δ| unde Δ=[tex] \left|\begin{array}{ccc}2&0&1\\0&4&1\\1&6&1\end{array}\right|[/tex] = 8+0+0-4-12-0=8-16=-8
A=1/2*|-8| = 1/2*8=4
