Question

use point slope formula to find the y-intercept.
the points are (1,2) and (-2,4). i found the slope, it is -2/3.

Answer 1

i started doing it but then when i came to 2y-4 = -4/3x - 4/3 i am stuck

Answer 2

can you work it out

Answer 3

slope formula

y2 - y1
-------
x2 - x1

you have points (1,2) and (-2,4)
(x1,y1) (x2,y2)

Answer 4

i already did that.. i got the slope.. it is -2/3.

Answer 5

now i need to find the y-intercept so i can write the equation of the line in standard form.

Answer 6

ok, I see you got the slope

Answer 7

no you need to find the value of b on formula y = mx + b

so you have m= -2/3
use any of the 2 points for x and y and find b

Answer 8

I meant now

Answer 9

im using the point- slope formula..

Answer 10

so u can use that instead?

Answer 11

oh, ok so you are using y - y1 = m(x - x1)

Answer 12

no nevermind

Answer 13

ill use the easier way

Answer 14

ok , so i have 2= -2/3(1)+b

Answer 15

it is easier with y = mx + b

Answer 16

that is good so what is the value of b

Answer 17

did you find b yet ?

Answer 18

no

Answer 19

i was away

Answer 20

how do you get it, i dont understand

Answer 21

is -2/3 *1 -2/3 ?

Answer 22

yes

Answer 23

ok so now idk what to do

Answer 24

2= -2/3 +b

Answer 25

y = mx + b
2 = -2/3(1) + b
2 = -2/3 + b (add 2/3 to each side)
2 + 2/3 = b
6/3 + 2/3 = b
can you get it now ?

Answer 26

ok

Answer 27

8/3 = b

Answer 28

yes

Answer 29

now how do i put it in standard form

Answer 30

points are (1,2) and (-2,4)

Answer 31

oh wait we dont need that info anymore

Answer 32

slope is -2/3 and y-int is 8/3

Answer 33

yes

Answer 34

you now have y = -2/3 x + 8/3

One good first step is "clear the fractions" by multiplying both sides (and all terms ) by 3

Answer 35

*update* guys, we've already found the y-intercept. now i need to write the standard form of the line.

Answer 36

so, 3(y= -2/3+8/3) ?

Answer 37

yes

Answer 38

but there is an x in there next to the -2/3

Answer 39

3y = -2x+8

Answer 40

now divide by 3?

Answer 41

Ax + By = C
y = -2/3x + 8/3 (multiply by 3)
3y = -2x + 8
now add 2x to both sides and what do you get ?

Answer 42

standard form is Ax + By = C
A is positive, and an integer.

no, dividing by 3 is "going backwards"

just add 2x to both sides and simplify

Answer 43

ok

Answer 44

so i add 2x to 3y and 8?

Answer 45

-2x i mean

Answer 46

like this
2x+ 3y = -2x + 8 +2x

Answer 47

now what

Answer 48

you see how the 2x's cancel each other out on the right side

Answer 49

on the right side you have 2 x's take away 2 x's that can be simplified to 0

Answer 50

now what are you left with

Answer 51

2x+3y = 8

Answer 52

you got it :)

Answer 53

finally :)

Answer 54

good job

Answer 55

Just for reference, you said
***when i came to 2y-4 = -4/3x - 4/3 i am stuck***
First, that should be
\[y- 4= -\frac{2}{3}\left( x - (-2)\right) \\ y- 4= -\frac{2}{3}\left( x +2\right) \\ y-4 = -\frac{2}{3}x -\frac{4}{3}\]
if you are trying to put that into y = mx+b form, you want the y "by itself"
the first step is add +4 to both sides
\[ y-4+4= - \frac{2}{3}x - \frac{4}{3} +4 \]
the left side simplifies to y
the right side has (unfortunately) fractions. Make 4 an improper fraction by multiplying by 3/3
you get
\[y= - \frac{2}{3}x - \frac{4}{3} + \frac{12}{3} \]
combine 12/3 - 4/3 to get 8/3:
\[ y= - \frac{2}{3}x + \frac{8}{3} \]