Y-Intercept (Mathematics Glossary)
What Is the Y-Intercept?
What Is the Y-Intercept of a Line?
The y-intercept of a line is the y-coordinate of the point where the line crosses the y-axis.
The line below crosses the y-axis at y = 3. The y-intercept of the line is 3.
The Y-Axis Crosses the X-Axis When X = 0
The y-axis crosses the x-axis when x = 0.
This means that all points on the y-axis have x = 0.
This is useful, because it let's us find the y-intercept of a line or a curve when we know its equation.
Finding the Y-Intercept of a Line from a Linear Equation
The y-intercept of a line can be found from the equation of a line (called a linear equation).
The slope-intercept form of a linear equation is:
In this equation, y and x are variables. m and c are letters that stand in for numbers. An example of a linear equation would be y = 2x + 1 (the m = 2 and c = 1).
The y-intercept occurs when the line crosses the y-axis. On the y-axis, x = 0.
The y-intercept of this equation is c.
Finding the Y-Intercept of a Line from a Function
The linear equation is an example of a function. For any value of x, it tells you y.
We can find the y-intercept of any function by substituting x = 0.
More About the Y-Intercept
The slider below gives more information about the y-intercept: