Question

PLEASE HELP!
Determine the equation of the line that passes through B(3,-1) and is perpendicular to the line defined by 2x+y-9=0.

Answer 1

First you need to put the equation into y=mx + b form. Do you know how to do this?

Answer 2

Are we suppose to take out the 0?

Answer 3

Yes you just need to isolate y.

Answer 4

y=2x - 9?

Answer 5

Close your signs are wrong though

Answer 6

which ones are wrong?

Answer 7

Remember when you want to move stuff around you need to do the operation so you are taking away 2x from each side and adding 9 to each side so it cancels on the left and is moved to the right understand?

Answer 8

It should be y = -2x + 9 know what I mean?

Answer 9

why are we puting 2x as a negative though?

Answer 10

Do you know how to do algebra?

Answer 11

Yes but, im so confused right now

Answer 12

Okay if you have y-5= 0 what does y= ?

Answer 13

Oh shoot sorry! I get it now

Answer 14

Since i want to transfer 2x and -9 to the other side i have to put it in the other operations as -2x and +9 right?

Answer 15

=) that's okay. So now we have it in the form we need that was step one next we need the negative inverse of the slop because a line that is perpendicular will have a negative inverse slope do you know how to find this? Yes that is correct =).

Answer 16

Would the -2x become as a 1/2? I dont know i did long time ago

Answer 17

Correct so now you know the slope of your perpendicular line do you want to write out what it looks like so far?

Answer 18

y= 1/2 + 9

Answer 19

Wait the slope of are new equation is (1/2) in y = mx +b the slope is "m" and we don't know what b is yet.

Answer 20

oh sorry!!!!! y=1/2x + 9

Answer 21

close

Answer 22

we don't know what b= so what should be in the place of b?

Answer 23

do we plug in (3,-1) to variables of x and y?

Answer 24

yes and solve for b because right now we have y = (1/2)x + b and we have a point on the line so we can solve for b like you said do you want to try that now?

Answer 25

y= 1/2x + 9
(-1) =1/2(3) + 9
(-1) =1.5 + 9
(-1) = 10.5
-11.5? i dont think this is right... :(

Answer 26

You don't know what b is you are trying to solve for b do you know what I mean?

Answer 27

you have y = (1/2)x + b you need to plug in your points and solve for b.

Answer 28

sorry!
y=(1/2)x + b
(-1) = (1/2)(3) + b
(-1) = (1.5) + b
(-1) - (1.5) = b
-2.5 = b

Answer 29

Looks good to me so what is your equation?

Answer 30

y= 1/2x - 2.5?

Answer 31

Correct =) good job

Answer 32

but it says in my book that it's x-2y-5=0....?

Answer 33

multiply everything by 2 and solve for zero to get it into that form. Doing this isn't changing the equation all the points will be the same.

Answer 34

That should say + 5

Answer 35

So the equation can be what we just did right? it doesn't have to be the form in which my book did it?

Answer 36

Not unless the teacher wants you to put it into that form.

Answer 37

Are you sure the one in the book doesn't say x - 2y + 5 = 0 ?

Answer 38

how do i put it in that form though? and no it doesnt say +5 :(

Answer 39

oh my bad sorry I got confused it should say -5 haha

Answer 40

Anyway you just multiply everything in the equation had by 2 and then you move everything to the left side and set the right to zero know what I mean?

Answer 41

not exactly...

Answer 42

2*y = 2*((1/2)x + 2.5) what does it look like after doing this?

Answer 43

2y=y +5 and the you put the x and 5 on the other side?

Answer 44

right =)

Answer 45

so its a 2y= -x -5?

Answer 46

wait look at what you typed

Answer 47

you need 2y - x - 5 = 0

Answer 48

So you don't put the equals sign?

Answer 49

what did the equation in the book say?

Answer 50

x-2y-5=0

Answer 51

okay so if you have 2y = x - 5 then you need to move the stuff on the right onto the left, and then you would have is -x+ 2y + 5 = 0 but what you need is x - 2y - 5= 0 so you multiply the equation by -1 and then you are done. Honestly these steps are pointless but it is just the way you make it look like the one in the book.

Answer 52

This is really confusing but i think i get it.... Why did you multiply by 2 in the first place though from the previous one?

Answer 53

In order to get the same coefficients

Answer 54

Oh alright, THANK YOU SO MUCH! :)

Answer 55

No problem you solved it =)