Then, to put this in point-slope form, substitute the slope for m, 0 for x 1, and b for y 1. Thus, the point we can derive from slope-intercept form is: Since we need one point to use point-slope form, we’ll need to find a point on the line.īecause we know the y-intercept of the line, which is the point where the line crosses the y-axis, we know a point on the line where x is equal to 0 and y is equal to the y-intercept. In slope-intercept form, the variable m is the slope, and b is the y-intercept. If you have an equation in slope-intercept form, you can convert it to point-slope form. X = c How to Convert Slope-Intercept Form to Point-Slope FormĪnother common way to express the equation of a line is using slope-intercept form. The variable c is the x-intercept of the line. Instead, the standard form equation can be used, where x is equal to a constant, c. Since vertical lines have an undefined slope, they cannot be represented using point-slope form. So, point slope form for a horizontal line looks like this:īy adding the y-coordinate to both sides of the equation, we can solve for y:Īnd this makes sense since every point on a horizontal line has the same y-coordinate, regardless of the x-coordinate.Ī vertical line where the line is parallel to the y-axis has infinite steepness, so the slope is undefined. A horizontal line is a line that is parallel to the x-axis, and has a slope of 0 since it has no steepness at all. Point-slope form can also be used to represent the equation of a linear horizontal line. It’s that easy to create the equation of a line. Since we know the slope and have a coordinate on the line, we can start with the second step and input 1/2 for the m variable, 3 for the x 1 variable, and 4 for the y 1 variable in the equation above. Lastly, in some cases, the equation can be reduced or simplified, and should be done so as a good mathematical practice.įor example, let’s create the equation for a line with a slope of 1/2 and a point (3, 4) in point-slope form. The next step is to substitute the slope and coordinates of one of the known points into the equation for the m, x 1, and y 1 variables, respectively. If you know the slope already, then you can skip this step. You can use the slope formula above to find it if you have the coordinates of two points on the line. The first step is to find the slope of the line. You can express the equation of a straight line in point-slope form in a few steps. Steps to Find the Equation of a Line in Point-Slope Form Note that the resulting equation of the line is now in the form of the point-slope formula above. The point-slope formula is derived from the slope formula.īy multiplying both sides of this equation by the denominator (x 2-x 1), the formula can be simplified to: Note that the slope is the coefficient of (x – x 1) in the formula. The point-slope form equation states that y minus the y-coordinate y 1 is equal to the slope of the line m times x minus the x-coordinate x 1. The point-slope form equation for describing a line is given by: Non-linear functions represent the equation of a curve, where the steepness of the function changes along the curve. Point-slope form is a linear equation of a straight line, so it is not useful for curves or line segments defined by piecewise functions. Point-slope form is most useful when you know the slope of a line and the coordinates of a point on the line. It is expressed using a standard formula. Point-slope form is an algebraic equation of a line using the slope and one point on the line. The calculator above will help describe the line in point-slope form. There are several standard equations for a line: point-slope form, slope-intercept form, and standard form. The most common way to describe a line is with an algebraic equation. However, the slope only describes the angle or gradient of the line, but not its position on a graph. One way to describe a line is using its slope, or gradient. When working with lines, there are a number of ways to describe the line.
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