Question

What is the equation of the line perpendicular to `y=21/4x` that passes through `(-3,5)`?

Answer 1

4x + 21y = 93

Explanation:

In the form y = mx + c for the equation of a straight line, m gives the slope of the line.

For any line perpendicular to this line, the slope is the negative reciprocal `-1/m`.

Here, m = `21/4`. `-1/m = -4/21`.
So, the equation of the perpendicular line through #(-3, 5) is #y-5 = (/4/21)(x + 3)#.

This can be rearranged as 4x + 21y = 93.