Question

Help please
What is the equation of the line perpendicular to –x + y = 7 and passing through (-1, -1)?

Answer 1

do you know how to write this in the form?

\[y = m(x)+b\]

Answer 2

@McFly_47

Answer 3

@Photon336 Is that the slope formula?

Answer 4

so yeah this is the formula for an equation of a line y = m(x)+b slope intercept form.

since we've got -x+y = 7

we need to first get y by itself how do we do this?

Answer 5

@Photon336 to be quite honest, I don´t know, can you help me?

Answer 6

@Photon336 x – y = 2 is this the answer?

Answer 7

here is what we do

we get y by itself and we do this by the following. see that -x we add it to both sides, doing the opposite operation.

-x+y = 7
+x +x

then we get

y = x+7

Answer 8

\[y_{1} = x+7 \]

now to find the line perpendicular to this, we need to take the -reciprocal of the slope.
We have 1 so it would be -1

so far

y = -x+?

okay, so far so good ?

Answer 9

so far so good sir

Answer 10

okay great. when the line must also pass through (-1,-1) have an idea of how to do this?

Answer 11

To be honest, no. I´m only 14 an they put me in this class and it is hard @Photon336

Answer 12

Can you teach me?

Answer 13

okay no problem so (-1,-1) means our x coordinate is -1 and our y coordinate is (-1)

Answer 14

so for the equation to pass through this point we must put the point in.

\[y = m(x)+b \]

\[y = -x+b\]

\[(-1) = -(-1)+b\]

we don't know what our b value is so we need to find it.

Answer 15

umm so b would count as 1 right?

Answer 16

and that I think would equal -2?

Answer 17

so let's check that

Answer 18

if b is -2 then our equation becomes this

\[y = -x-2 \]

now when we plug in -1 we should get -1 also

-(-1)-2

1-2 = -1

so this works

do you see this?

Answer 19

I see how that works, but, would that be the answer?
I have 5 options
-x + y = 2

-x – y = 2

x – y = 2

-x – y = 0

x + y = 0

Answer 20

@Photon336

Answer 21

so look at the second one

-x-y = 2

can you solve for y, or in other words get y by itself?

Answer 22

Adding y to both sides and then dividing by 2?

Answer 23

@Photon336

Answer 24

what would be our answer ?

Answer 25

x=−y−2 ?

Answer 26

is that right? @Photon336

Answer 27

watch what I do

Answer 28

-x-y = 2

we get y by itself.

see the -x

we add that to both sides and get

-y = 2+x

or

-y = x+2

Answer 29

now after we do this, we need to get that - sign away from that y

so it's actually this

\[-1*y = x+2 \]

so we divide everything by -1

\[y = -x-2\]

look familiar?

Answer 30

Yeah its like m answer but switching the x and y

Answer 31

yep so that's the answer

Answer 32

-x-y = 2

Answer 33

@Photon336 wow, thank you so much for your time, and this looks like a simple problem but it sure is hard

Answer 34

I'll show you how to work with the formula it's pretty simple.

Answer 35

@Photon336 I am so sorry my Internet went out, I would appreciate that

Answer 36

yeah, no problem

Answer 37

@Photon336 Just one question if its not too much to ask, how is the formula called?