y=ax+b
1) we put this points into general formula
[tex]\left \{ {{-1=a*0+b} \atop {8=6a+b}} \right.\\b=-1\\8=6a-1\\6a=9\\a= \frac{3}{2} [/tex]
[tex]y= \frac{3}{2}x-1 [/tex]
2)
[tex] \left \{ {{1=3a+b} \atop {7=9a+b}} \right. \\ b=1-3a\\7=9a+1-3a\\6a=6\\a=1\\b=1-3*1=-2\\y=x-2[/tex]
3)
[tex] \left \{ {{2=a+b} \atop {14=10a+b}} \right.\\b=2-a\\14=10a+2-a\\12=9a\\a= \frac{4}{3} \\b=2- \frac{4}{3}=\frac{2}{3}\\y=\frac{4}{3}a+\frac{2}{3}[/tex]
4)
[tex] \left \{ {{0=b} \atop {5=-3a+b}} \right.\\5=-3a\\a=- \frac{5}{3}\\y=-\frac{5}{3}a [/tex]
