Question

6. The equation of line A is 3x + 6y - 1 = 0. Give the equation of a line that passes through the

point (5,1) that is

/1 a. Perpendicular to line A

Answer:

/1 b. Parallel to line A

Answer:

Answer 1

Step 1: Convert to slope-intercept form to find the slope of the line.

This isn't necessary if you know all the shortcuts, it just makes your life a bit easier.


`3x+6y-1=0\\6y=-3x+1\\y=-(3)/(6)x+(1)/(6)\\-(1)/(2)x+(1)/(6)`

Now we want to find the equations for our new lines. It's easiest to do this in slope-intercept form, so let's start finding the slope and y-intercept.

So for the perpendicular line, the slope is going to flip and change signs, this is aka its opposite reciprocal.
And for the parallel line, it'll stay the same.


`-(1)/(2)` ⇒
`(2)/(1)=2`

`-(1)/(2)` ⇒
`-(1)/(2)`

As for the y-intercept, just apply that slope until you get a point where x=0.

(5, 1) with a rise of 2 and a run of 1...let's work backwards to (0, b)
(5, 1), (4, -1), (3, -3), (2, -5), (1, -7), (0, -9).

(5, 1) with a rise of -1 and a run of 2...let's work backwards to (0, b)
(5, 1), (3, 0), (1, -1)...gonna have to take half a step here...(0, -1.5).

Now let's construct our equations in slope-intercept form.


`y = 2x-9\\y=-(1)/(2)x-(3)/(2)`

And now it's time to convert to general form!

Make sure we have common denominators...check.

Multiply by the denominator...


`y=2x-9\\2y=1x-3`

...check.

Aaaand bring everything over!


`\boxed{-2x+y-9=0}\\\boxed{-x+2y-3=0}`