Standard Form for the Equation of a Line
Another form for the equation of a line is standard form. Standard form
is useful, for example, when solving sytems of equations.
Definition
Standard Form for the Equation of a Line
The standard form for the equation of a line in two variables is
Ax + By = C, where A, B, and C are real numbers, and A and B are not both zero.
The following linear equations are written in standard form:
5x + 3y = 7
x - 2y = -5 |
Here, A = 5, B = 3, and C = 7.
Here, A = 1, B = -2, and C = -5 |
Note:
When writing an equation in standard
form, the terms on the left must be
arranged in the form Ax + By. The x-term
is always written before the y-term.
2x + 5y = 3 is in standard form.
5y + 2x = 3 is NOT in standard form.
Example
Write the equation
in standard form.
Solution |
y + 4 |
|
To clear the fraction, multiply both
sides of the equation by the LCD, 2. |
2[y + 4] |
|
Simplify. |
2y + 8 |
= x - 6 |
Subtract 8 from both sides. |
2y |
= x - 14 |
Subtract x from both sides. |
-x + 2y |
= -14 |
The equation -x + 2y = -14 is in standard form.
Here, A = -1, B = 2, and C = -14. |
|