Question

What is an equation of the line that passes through the point

(
6
,
−
4
)
(6,−4) and is perpendicular to the line
2
x
−
y
=
5
2x−y=5

Answer 1

x + 2y = -2

Explanation:

Well let's examine the relation between x and y in a perpendicular line.

We can use the fact that for a line Ax + By = C, any line with equation Bx + (-A)y = D is perpendicular (swapping A and B gives a mirror image with respect to the line x=y and changing one of the signs gives a mirror image with respect to axis x or y. Those two together give a perpendicular line).

So we're looking for a line with equation x + 2y = D

We know what it passes through the point (6, -4), so let's input it into the equation x + 2y = D

6 + 2*(-4) = D

6 - 8 = D

D = -2

So the equation is x + 2y = -2

note that 2x + 4y = -4

or any other multiple also works.