ANSWER
f(x) = 3x - 6
EXPLANATION
The equation of a line is:
[tex]f(x)=mx+b[/tex]where m is the slope and b is the y-intercept.
The formula for the slope of a line passing through points (x1, y1) and (x2, y2) is:
[tex]m=\frac{y_1-y_2}{x_1-x_2}[/tex]So the slope for this line is:
[tex]m=\frac{0-6}{2-4}=\frac{-6}{-2}=3[/tex]For now we have :
[tex]f(x)=3x+b[/tex]To find the y-intercept b we have to replace with one of the points and solve for b:
[tex]\begin{gathered} f(2)=0=3\cdot2+b \\ 0=6+b \\ b=-6 \end{gathered}[/tex]So the equation is:
[tex]f(x)=3x-6[/tex]