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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


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)
equation of a straigth line - online calculator

The slope of the line through points (x1, y1) and (x2, y2) is given by
= (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)

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Enter two points...

Point 1 = (, )
Point 2 = (, )

slope m =
y-intercept b =

Enter the slope and one point...

slope m =
(x, y) = (, )

y-intercept b =

Enter slope, y-intercept and a value...

slope m =
y-intercept b =
value =

(value, y) = ()
(x, value) = ()

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