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Parallel Line Equation Calculator

Find the equation of a line that runs parallel to a given line and passes through a specific point. This calculator helps you understand the relationship between parallel lines and their slopes.

Enter the slope of the line you want to be parallel to.

Enter the x-coordinate of the point the new line passes through.

Enter the y-coordinate of the point the new line passes through.

How it works

Find the equation of a line that runs parallel to a given line and passes through a specific point. This calculator helps you understand the relationship between parallel lines and their slopes.


The Formula
A line parallel to y = mx + c has the same slope 'm'. Using the point-slope form y - y₁ = m(x - x₁), you can find the new equation.

Worked Example
  1. Parallel to y = 2x + 5 through (3, 1)

    To find the equation of a line parallel to y = 2x + 5 that passes through the point (3, 1): The slope of the given line is m = 2. Using the point-slope form y - y₁ = m(x - x₁), we substitute m=2, x₁=3, and y₁=1. So, y - 1 = 2(x - 3). This simplifies to y - 1 = 2x - 6, which gives y = 2x - 5.


Tips, Assumptions & Limitations
  • Remember that parallel lines always have the same slope.
  • Use the point-slope form (y - y₁) = m(x - x₁) to build the new equation.
  • The y-intercept of the original line does not affect the slope of the parallel line.
FAQ

Two lines are parallel if they lie in the same plane and never intersect. The defining characteristic of parallel lines is that they have identical slopes. If one line has a slope of 'm', any line parallel to it will also have a slope of 'm'.

To find the slope from an equation in the form Ax + By = C, you need to rearrange it into the slope-intercept form (y = mx + c). Subtract Ax from both sides: By = -Ax + C. Then, divide by B: y = (-A/B)x + (C/B). The slope 'm' is -A/B.

This calculator is designed for lines that can be expressed in the slope-intercept form (y = mx + c). Vertical lines have an undefined slope and their equations are typically in the form x = k (where k is a constant). This tool does not directly handle vertical lines, but a line parallel to x=k would also be x=k' (another vertical line).

Companion article

Equation of a Parallel Line Calculator: Find Your Line's Twin

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