Question

What is the equation for a line that goes through points (-4,0) and (8, 12)

A.y=1x+4
B.y=-1x+4
C.y=1x+6
D.y=1x+3


please explain what you did

Answer 1

first you need the slope

Answer 2

so you use this formula

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

to get the slope

Answer 3

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


m = (12 - 0)/(8 - (-4))


m = (12 - 0)/(8 + 4)


m = ???

Answer 4

Tell me what you get for the slope.

Answer 5

I got 12/12 but I've never been good with slopes so it is probably wrong

Answer 6

12/12 is correct

which simplifies to 1

Answer 7

so the slope is m = 1

Answer 8

Now move onto the general form y = mx+b

y = mx+b

y = 1x + b ... plug in m = 1

0 = 1(-4) + b ... plug in x = -4 and y = 0 (from the first point (-4, 0))

0 = -4 + b

0+4 = b

4 = b

b = 4

---------------------------------

So we now know that m = 1 and b = 4

which means

y = mx+b

turns into

y = 1x + 4

Answer 9

so it would be A

Answer 10

that is correct

Answer 11

Notice how the point (8,12) is on this line

y = 1x + 4

12 = 1(8) + 4 ... plug in x = 8 and y = 12 (from the point (8,12))

12 = 8 + 4

12 = 12

which is true, so that verifies that (8,12) is on the line

Answer 12

So if I were to show my work it would be written like this:

Answer 13

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


m = (12 - 0)/(8 - (-4))


m = (12 - 0)/(8 + 4)


m = 1

y = mx+b

y = 1x + b ... plug in m = 1

0 = 1(-4) + b ... plug in x = -4 and y = 0 (from the first point (-4, 0))

0 = -4 + b

0+4 = b

4 = b

b = 4

m = 1 and b = 4

y = 1x + 4

Answer 14

@jim_thompson5910

Answer 15

sry for some reason the notifications system on here isn't working (idk why)

Answer 16

Its fine

Answer 17

but yeah, you first show how to get the slope

Answer 18

then you show how to use that slope, and one of the two given points, to find the y-intercept

Answer 19

Okay. Thank you so much for the help :)

Answer 20

you're welcome