Equation of Straight Line in Plane/Two-Intercept Form

Theorem
Let $\LL$ be a straight line which intercepts the $x$-axis and $y$-axis respectively at $\tuple {a, 0}$ and $\tuple {0, b}$, where $a b \ne 0$.

Then $\LL$ can be described by the equation:
 * $\dfrac x a + \dfrac y b = 1$

Also known as
This form of the Equation of Straight Line in Plane is also known as the intercept form.