  # Equation of a straight line  -  online calculator

Below you can use a calculator prepared to find the equation of a straight line. A line in a Euclidean space of dimension n is the set of the points whose coordinates satisfy a given set of n−1 independent linear equations.

 A line segment is a part of a line that is bounded by two different end points and contains every point on the line between its end points. In analytic geometry, lines in a Cartesian plane can be described algebraically by linear equations and linear functions. In two dimensions, the characteristic equation is often given by the slope-intercept form:

 y = mx + b where: m is the slope of the line b is the y-intercept of the line x is the independent variable of the       function y = f(x) The slope of the line through points (x1, y1) and (x2, y2) is given by
m
= (y2 – y1)/(x2 – x1), and the equation of this line can be written
y = m(xx1) + y2 (notice that b = y2).

This calculator has three sections: a) you enter two points, and the calculator returns slope (m) and intersect (b); b) you enter slope (m) and one point (x, y), and the calculator returns intersect (b); c) you enter slope (m) and one value (either x or y), and the calculator interpolates to deliver two points, both (value, y) and (x, value).

### Example 1 - You know two points; calculate the slope and the y-intercept:

If you know two points that are on your line, the calculator returns m and b. For points (0, 1) and (0.25, 0), you fill in the blanks

Point 1  = (0     1)
Point 2  = (0.25  0)

and you get

m = -4.0000
b =  1.0000

### Example 2 - You know the slope and the y-intercept; calculate any two points on the line:

If you know the slope and the y-intercept, you can obtain the value of the function at any x or y-value. For a given m = -4 and b = 1, you can enter value = 1 (which means in this case both x = 1 and y = 1), like this:

m = -4
b = 1
value = 1

and you get points (x, y), first when x = value, and then when y = value.

(value, y) = (1.0000, -3.0000)
(x, value) = (0.0000, 1.0000) 