When creating a table of values for the function, you may not have taken into account the addition of the constant $\displaystyle-{2}\usepackage{cmbright}\Huge\$ . This graph matches the function $\displaystyle{f{{\left({x}\right)}}}={3}{x}\usepackage{cmbright}\Huge\$ , not $\displaystyle{f{{\left({x}\right)}}}={3}{x}-{2}\usepackage{cmbright}\Huge\$ .