[tex]Fie~f:R-\ \textgreater \ R, f(x)=a*x+b,A,B\in Gf \\ \\ A\in~Gf\ \textless \ =\ \textgreater \ f(1)= \frac{7}{2} \\ \\ B\in~Gf\ \textless \ =\ \textgreater \ f(-2)=8 \\ a+b= \frac{7}{2} \\ -2a+b=8 ~(*)\\ 2a+2b=7~(**) \\ 3b=15 \\ b=5 \\ a= \frac{-3}{2} \\ f(x)=- \frac{3}{2} x+5 \\ Ca~cele~trei~punte~sa~fie~coliniare~,~trebuie~ca~C~sa~apartina~ \\ graficului. \\ C\in~Gf\ \textless \ =\ \textgreater \ - \frac{3}{2} * \frac{10}{3} +5=0 \\ -5+5=0(Adevarat!) \\ \\ Deci, sunt ~coliniare! \\ La~b)~faci~acelasi~lucru![/tex]
