How to Write a slope-intercept equation perpendicular to line

In this tutorial the instructor shows how to write a Slope-intercept equation that is perpendicular to a line and passes through a point. He shows how to do this by solving an example with sample values. He says that the slope of a line perpendicular to the original line is the negative inverse of the slope of original line. Now he writes down the slope value in the general equation y = mx + c, and by substituting the sample value in the equation he obtains the value of the Y-intercept c, thus arriving at the equation of the final line. This video shows how to write an equation in slope-intercept from that passes through a given point and is perpendicular to the given line.