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...)
Other useful lessons:
 Calculating equation of a line from two points Calculating equation of a line from slope and intercept Calculating equation of a line from point and intercept Determine whether a point lies on a line
(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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