Question

The line that passes through the given point and is perpendicular to the given line in slope intercept form: (1,-9) 4x+8y=12

Answer 1

First, rewrite the line in slope intercept form.

Answer 2

Okay will it be um y=2x+3/2 ??? im not positive about it

Answer 3

Almost. Divide everything in the equation by 4 first.

Answer 4

And then isolate y.

Answer 5

Ok I did I got y=1/2x+3/2

Answer 6

Yup. So one trick with perpendicular equations is that the slope is always the negative reciprocal of the current slope.

Answer 7

So if your slope is 2, then the perpendicular slope is -1/2.

Answer 8

So in this case, your slope is 1/2, which means the perpendicular slope is -2.

Answer 9

Got it and is the slope always going to come up as a fraction?

Answer 10

Not necessarily, it depends on what your original slope was. If your original slope was a fraction, then the perpendicular slope may be an integer or a fraction, depending on what the fraction was.

i.e. 10/7 would become -7/10 but 1/10 would become -10

And we know that the slope intercept form of a line is y = mx +b.

Now we have the slope as well as a point.

So substitute everything into the equation to find b.

Answer 11

b=-19/2

Answer 12

So now you know your slope and the value of b. All you have to do is put it in y = mx + b form!

Answer 13

so then the slope intercept form will be y=1/2x-19/2 ??

Answer 14

am i right?

Answer 15

Almost. Your original slope was 1/2, right?

Answer 16

yes

Answer 17

So the slope of the perpendicular line will be the negative reciprocal, which means it will be -2.

Answer 18

that'll mean it will y=-2-19/2 ??

Answer 19

You forgot the x, but yes.

Answer 20

WHOOHOO!! haha:) and lets say the slope will be -2 then what will the reciprocal be?

Answer 21

1/2

Answer 22

oh
the reciprocal?

The reciprocal is just -1/2

Answer 23

if you have a value n, then the reciprocal is just 1/n

Answer 24

thanks will you mind helping me in another problem?

Answer 25

I'll write it in another post though