What is the equation of the line perpendicular to y=9/20x that passes through (-1,-5) ?

1 Answer
Apr 27, 2018

Find the negative reciprocal of the slope of our given equation,
y=9/20x.

Keep in mind that the slope of any line is defined as the negative reciprocal of the slope of the line that it is perpendicular to.

The negative reciprocal of 9/20 is -20/9. This is the slope of our perpendicular line.

This perpendicular line also lies on the point (-1, -5). With the coordinates of this point and the slope we previously found, we can construct our answer in point slope form:

y-y_1 = m(x-x_1), where m = slope, x_1 and y_1 are the x and y-coordinate of the point (x_1, y_1) respectively.

In our case, m = -20/9, x_1 = -1, and y_1 = -5.

Now all we must do is to simply plug in our values:
y+5=-20/9(x+1)

If the question requires an equation in slope-intercept form, simply subtract 5 from both sides and simplify!