<em>Greetings from Brasil...</em>
As we have a line, the function will be given by the expression:
F(X) = AX + B
where
<em>A = ΔY/ΔX</em>
<em>B = where the line intersects the Y axis</em>
Looking at the graph we have already concluded that
B = - 3
A = ΔY/ΔX
A = (5 - 3)/(4 - 3) see attached picture
A = 2
So,
F(X) = AX + B
<h2>F(X) = 2X - 3</h2>