Question

Write an equation for the line that passes through the points (0, -2) and (-4, 0).
y= -2x- 4
y= -2x- 2
y= -1/2x - 2
y= -1/2x - 4

I believe it is y= -2x- 4, but I just want to make sure so I can see if I did something wrong.

Answer 1

if you plugged x = 0 into y = -2x - 4, what would you get for y?

Answer 2

It would be y= -2(0) - 4 I get, but I'm still confused.

Answer 3

evaluate the right side

Answer 4

do you know what I mean by that?

Answer 5

Multiply -2(0)?

Answer 6

to get what

Answer 7

Y?

Answer 8

-2 times 0 = ???

Answer 9

0.

Answer 10

so -2(0) - 4 turns into 0 - 4

Answer 11

simplify 0-4 to get what number

Answer 12

And you would simplify 0-4 by adding..I think, I'm confused again.

Answer 13

no you just subtract

Answer 14

0 - 4 = -4

Answer 15

so if we started with y = 2x - 4, plugged in x = 0, we would get this


y = -2x - 4


y = -2(0) - 4


y = 0 - 4


y = -4

Answer 16

what does this mean?

Answer 17

My answer was correct?

Answer 18

no it means that the point (0,-4) is on the line

but we want (0,-2) to be on the line

Answer 19

see the difference?

Answer 20

would you use the slope formula first to find the slope ?

Answer 21

yes that's one way to go about it texaschic101

but since we have answer choices, we can take advantage of that

Answer 22

ok...I understand

Answer 23

No, I'm still confused a little.

Answer 24

the idea is this: the two points must be on the line (both of them must be)

so if you plugged each point one at a time, it should make the equation true (for both points)

Answer 25

would it be easier to show her the slope formula in case she has other questions that don't include answer choices ?

Answer 26

y = 2x - 4

-2 = 2(0) - 4 ... plug in (0,-2)

-2 = 0 - 4

-2 = -4 ... that's false, so (0,-2) is NOT on the line

Answer 27

yes that's probably the best way to do it since multiple choice won't always be there

Answer 28

Oh, I get that part now.

Answer 29

I am not trying to take over your explaining jim.....its all yours

Answer 30

oh thanks, wasn't sure if you wanted to go or not lol

Answer 31

anyways, the slope formula is this

m = (y2 - y1)/(x2 - x1)

Answer 32

the two points are: (0,-2) and (-4,0)

so,

(x1,y1) = (0,-2) ----> x1 = 0 and y1 = -2

(x2,y2) = (-4,0) ----> x2 = -4 and y1 = 0

we then plug all this into the slope formula

Answer 33

m = (y2 - y1)/(x2 - x1)

m = (0 - (-2))/(-4 - 0)

m = (0 +2)/(-4 - 0)

m = (2)/(-4)

m = -1/2

so the slope is m = -1/2

Answer 34

Listen to him Kelli....he is good

Answer 35

this means that the answer cannot be y = 2x - 4 since the slope for y = 2x - 4 is 2 (not -1/2)

so we can effectively eliminate choices A and B

Answer 36

with me so far?

Answer 37

Yes, I'm with you so far, it's all just very confusing for me sometimes with all the numbers and etc.

Answer 38

yeah it's a lot to keep track of

Answer 39

but you'll get the hang of it

Answer 40

we know that the slope is m = -1/2

one point is (0, -2), let's use this to find the y-intercept b

y = mx + b

y = (-1/2)x + b ... plug in the given slope

-2 = (-1/2)(0) + b ... plug in (0,-2)

-2 = 0 + b

-2 = b

b = -2

So the equation y = mx+b turns into y = -1/2x - 2

Answer 41

I get it now, thank you.

Answer 42

ok great, keep practicing it and you'll be a pro at it in no time