Question

What is the y−coordinate of the y−intercept of the line that passes through the points (−4, −4) and (4, 8)?

Answer 1

ok so the best thing we can do is to find the equation of this line

Answer 2

can you find the slope of this line ?

Answer 3

how do you find it again??

Answer 4

i havent done this is so long..:/

Answer 5

in*

Answer 6

ok so slope : m = (y1 - y2) / (x1-x2)

Answer 7

oh oh ok let me try

Answer 8

-4-8=-12 and -4-4=-8 so -12over-8?

Answer 9

yes .. which is 1.5

Answer 10

now.. find line equation by :
y = y1 + m(x-x1)

(x1,y1) may be one of your two points that you got

Answer 11

wait what? :P

Answer 12

y = y1 + m(x-x1) -> if you use this formula you can get the line equation
in our case we can choose x1 = -4 , y1 = -4
or
x1= 4 ,y1 = 8

Answer 13

so the anwser is 4,8?

Answer 14

or wait? yah no...im lost..im sorry :(

Answer 15

ok again .. we need to find y intercept

Answer 16

its the point where x=0 right ?

Answer 17

i thnk soo yes

Answer 18

so what i want to do is to find the equation of the line
what it means is that in this equation i will be able to plug x =0
and get the y-intercept
or any other x that i want to find the corresponding y of it

Answer 19

we already found the slop of this line m = 1.5

Answer 20

yes

Answer 21

now if you have a point that the line passes through and you got also the slope of the line
you could find the equation that describes the line
using this formula :
y = y1 + m(x-x1)
where m - slope
(x1,y1) a point that the line passes through

Answer 22

oh ok so it could be y=8+1.5(4+4) ?

Answer 23

?

Answer 24

why ? look at the formula 1.5(x-x1)
so
y=8+1.5(x-4)

Answer 25

do you understand why ? x for us is anything we want
in this case we would like to plug x=0 since we want y intercept

Answer 26

okk

Answer 27

now y=8+1.5(x-4) this is our line equation
replace x by 0 and you will get y intercept ..
do you understand what we have done ?

Answer 28

yes i think so..so y=8+1.5(0)-6 ?

Answer 29

yes y intercept would be 2

Answer 30

ohhhhhh thats the anwser!! :) thank you! can you help me with a few more??

Answer 31

yes but you must understand .. try to do it by your self and tell me where you stuck

Answer 32

okay the questions i put up here i dont understand..:P let me tryyy