.. Copyright (C) Google, Runestone Interactive LLC This work is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/4.0/. .. _equation_of_a_line_refresher: Equation of a Line (Refresher) ============================== .. image:: figures/equation_of_a_line.png :align: center :alt: Slope intercept form: y equals m times x plus b. All line equations in this text will be presented in the form *y = mx + b*, where *m* is the slope and *b* is the y-intercept. This is also called slope-intercept form. The **y-intercept** is the y-value at the point where the line crosses the y-axis. The :ref:`slope ` gives the steepness of the line, and can be positive, negative, or zero. Slope-intercept form is a method to better understand the relationship between the two variables *x* and *y*. .. image:: figures/negative_slope.png :width: 49% :alt: A graph of the equation y equals negative one third times x plus five and the slope is negative. This figure depicts an equation of a line that has a y-intercept of 5 and a negative slope. .. image:: figures/positive_slope.png :width: 49% :alt: A graph of the equation of y equals 2 times x plus one. The equation of the line in the above figure has a y-intercept of 1 and a positive slope. For additional review on slope-intercept form you can also watch out `this video `_.