Question

Write the equation of the line perpendicular to x+2y=6 that passes through (5, 8).

Answer 1

y = 2x - 2

Explanation:

x + 2y = 6 can be solved for y (and thus for slope m) as follows:

2y = -x + 6, or y = (-1/2)x + 3.

Any new line perpendicular to this one has a slope that is the negative reciprocal of (-1/2); that would be +2.

Starting from y = mx + b,

Replace x with the given 5, y with the given 8 and m with the calculated +2:

8 = 2(5) + b, or

b = -2

and then the desired equation is

y = 2x - 2

Answer 2

y = 2x-2

Explanation:

First find the slope of the line

x+2y=6

2y = -x+6

y = -1/2x +3

This is in slope intercept form ( y = mx+b) so -1/2 is the slope

We want a line that is perpendicular so take the negative reciprocal of the slope

- ( 1/ (-1/2)) = 2

The slope of the perpendicular line is 2

y = 2x+b

Substitute the point into the equation

8 = 2(5) +b

8 = 10+b

-2 =b

The equation of the line perpendicular is

y = 2x-2