Question

Can someone explain a bit to me about the equations of lines? :)

Answer 1

what do you need to know ?

Answer 2

the equations of the lines?

Answer 3

Oh, I just want to know what you would do for slanted lines?

Answer 4

I get horizontal and vertical lines. :)

Answer 5

u need to find the slope.

Answer 6

lets use an example.
a line with points (3,2) and (9,0)

Answer 7

Okay I got that so far. :)

Answer 8

now do u know how to find the slope?

Answer 9

Wouldn't it be y2-y2/x2-x1. ;)

Answer 10

I meant y2-y1/x2-x1

Answer 11

yes.
so set one of the points as x1, x2 and the other one as x2, y2

Answer 12

the points are (9,0) and (3,2)

Answer 13

So the slope would be -1/3?

Answer 14

yes. good job

Answer 15

now use one of the points to find the y intercept.

Answer 16

use the slope equation like this: \[\frac{ 0-x }{ 9-0 }= \frac{ -1 }{ 3 }\]

Answer 17

and solve for x.

Answer 18

cross multiply first.

Answer 19

Oh, that's kind of confusing. :(

Answer 20

9-0*1 would be 9, right? :)

Answer 21

multiply whats in the denominator of one side of the equation to the top of the other side

Answer 22

well first we can simplify the equation to get \[\frac{ -x }{ 9 }=\frac{ -1 }{ 3 }\]

Answer 23

So -3x=-9

Answer 24

yes.

Answer 25

so try to simplify that a little more.

Answer 26

-3x=-9
x= 3

Answer 27

yes. so (0,3) would be the y-intercept.

Answer 28

Oh, okay, that makes sense, thank you! :)

Answer 29

to get the equation of the line, use the slope intercept formula.

Answer 30

Isn't that y-y1=m(x-x1)?

Answer 31

which is...\[y=ax\]

Answer 32

no thats the point slope formula.

Answer 33

y=ax+b i mean

Answer 34

a is the slope and b is the y intercept.

Answer 35

so lets plug in the right numbers.

Answer 36

Oh, all right. :) -1/3x+3

Answer 37

Is that it? :)

Answer 38

Do you have a specific question?
if you want background, see
http://www.khanacademy.org/math/algebra/systems-of-eq-and-ineq/fast-systems-of-equations/v/solving-linear-systems-by-graphing

Answer 39

/[y=\frac{ -1x }{ 3 }+3]

Answer 40

thats it

Answer 41

there are other equations to find it, but if you have 2 points, u can find the equation.

Answer 42

Okay, thanks, @phi and @DavidUsa

Answer 43

if u have only one point and the slope, u can always find another point and use the slope intercept formula.

Answer 44

Thanks soo much for ur help, @DavidUsa I really appreciate it. :)

Answer 45

yea no problem

Answer 46

ur welcome

Answer 47

:D