Calculating equation of a line from point and slope

Algebra I: Calculating equation of a line from point and slope

This is a free lesson from our course in Algebra I


	This lesson explains how to write the equation of a line if you know its slope and a point on it. This form of equation of a line is called the point-slope form. As you'll see, equation of a line with slope m and passing through a point (a, b) is given by y - b = m(x - a) Somewhere, you'll find a point as (x₁, y₁) and a slope m, and a formula: y � y₁ = m(x � x₁) Here subscripts are just intended to indicate the point given. You have the generic "x" and generic "y" that are always in your equation, and then you have the specific x and y from the point given; the specific x and y are what is subscripted in the formula. (More text below video...)

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	(Continued from above) For example : Find the equation of the straight line that has slope m = 4 and passes through the point (1,1). You've given m = 4, x₁ = 1, and y₁ = 1. You'll plug these values into the point-slope form, and solve for "y=": y � y₁ = m(x � x₁) y � (1) = (4)(x � (1)) y -1 = 4(x - 1) y - 1 = 4x - 4 y = 4x - 4 + 1 y = 4x � 3

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