The points \( (a, 0) \) and \( (b, a) \) lie on the line \( y = f(x) \) and so an equation to the line is
\[ f(x) = \dfrac{6}{b - a} (x - a) \]
Similarly, an equation for the line \( y = g(x) \) is
\[ g(x) = \dfrac{2}{b - a}(x - a) \]
If \( x \neq a \), then \( g(x) \neq 0 \) and \( \dfrac{f(x)}{g(x)} = 3 \). Therefore, \( \displaystyle\lim_{x \to a} ~ \dfrac{f(x)}{g(x)} = 3 \).
This limit can also be evaluated using similar triangles.