Question

write the equation of the line in point-slope form. (-2,4) and (-5,6). i found the slope, it is 2/-3.

Answer 1

I am looking for the y-intercept so this is what i have so far:

Answer 2

y= mx+b
4= 2/-3(-2)+b

Answer 3

then its 4= -4/-3 +b no idk what to do

Answer 4

this site helps sometimes try it http://www.wolframalpha.com/

Answer 5

but if you want an explanation ask someone

Answer 6

it gave me 4= b+ 4/3 which is 8/3

Answer 7

now how do i use the slope 2/-3 and b which is 8/3 to make an equation of the line in point-slope form

Answer 8

ok you have

4 = -2/3 (-2) + b

4 = 4/3 + b

4 4 12 -4 8
-- - --- = ----- = ------
1 3 3 3


so b = 8/3

Answer 9

now just plug in on formula y = mx + b
y = -2/3x + 8/3

Answer 10

noo i need point slope formula.

Answer 11

"2.Determine the equation of the line in point-slope form"

Answer 12

y - y1 = m(x - x1) (this formual ?)

Answer 13

yes

Answer 14

then you have m = -2/3 and (x,y) could be any known point
you have point (-2,4)

so it is y - 4 = -2/3(x + 2)

Answer 15

so.. y-4= -2/3 x then what

Answer 16

If they want point - slope form, you do not need to first find y= mx + b (slope-intercept form)

instead, find the slope, which you did
and then pick one of the points, and use that point in

\[ y - y_1= m(x-x_1) \]

Answer 17

y-4= -2/3 x + -4/3 right?

Answer 18

ohh so i did an extra step woops

Answer 19

Don't distribute. point-slope form is just
\[ y - y_1= m(x-x_1) \]
leave it that way

Answer 20

ohh

Answer 21

r u sure

Answer 22

is just y - 4 = -2/3(x + 2)

Answer 23

http://www.mathsisfun.com/algebra/line-equation-point-slope.html

Answer 24

y - y1 = m(x - x1)
do not distribute...just leave it , parenthesis and all

Answer 25

ok

Answer 26

i have a few more questions im gonna put the next one

Answer 27

point-slope form is not very useful (for plotting for example) but it is easier to write down (less algebra).

Answer 28

yes

Answer 29

my next one is Determine the equation of the line, in slope-intercept form

Answer 30

the points are:

Answer 31

(-5,6) and (-8,8)

Answer 32

this one is y = mx + b
which you have done already
first find the slope,
then solve for b

Answer 33

for slope i got 2/-3

Answer 34

so i plug in a point, and the slope, to solve for b?

Answer 35

yes

Answer 36

ok ill use (-5,6)

Answer 37

ok i got 6= -10/-3 +b

Answer 38

so that's like the same as 6= 10/3 +b right

Answer 39

yes. now add -10/3 to both sides

Answer 40

10/3 u mean

Answer 41

6= 10/3 +b

add -10/3 to both sides

Answer 42

because you want 10/3 - 10/3 = 0 so you get 0+b on the right side

Answer 43

wait wait ur confusing me, look what ur writing. first u write 10/3 then u write -10/3.. which is it?

Answer 44

here is what you did:
ok i got 6= -10/-3 +b

so that's like the same as 6= 10/3 +b right

yes, that is correct:
6 = 10/3 + b

now to solve for b, add -10/3 to both sides

Answer 45

see u did it again

Answer 46

u wrote "now to solve for b, add -10/3 to both sides" do u see the problem here?

Answer 47

but just before you wrote 6= 10/3 +b

Answer 48

y would i add -10/3 to both sides if we just made the fraction simpler by taking away the negatives?

Answer 49

do i add or subtract

Answer 50

if would have been less confusing if u said subtract 10/3 from both sides

Answer 51

so now whats 6 - 10/3 ?

Answer 52

you agree we started with
y = - 2/3 x + b
you picked point (-5,6) and got

6 = - 2/3 * -5 + b which becomes
6 = 10/3 + b

so far, so good.

now add -10/3 to both sides. Can you do that ?

Answer 53

to do fractions, you need a common denominator. in this case, 3
to get a denominator of 3 for 6, multiply 6 times 3/3
you get 18/3
now you can do the fractions

Answer 54

so b is 18/3 ??

Answer 55

you should get
b= 6 - 10/3

change 6 to 18/3
b= 18/3 - 10/3

to add or subtract fractions with the same bottom, add or subtract the tops
18 -10 = 8
and put that number over the common denominator

Answer 56

so 8/3

Answer 57

yes

Answer 58

It looks like all the points are ending up on the same line

y= -2/3 x + 8/3 looks familiar

Answer 59

yup

Answer 60

because they are. i made it that way

Answer 61

we had to pick three points and make them be in the same line as (1,2) the "launch area" for a project.

Answer 62

and then you have to find the different ways to write an equation of a line: standard, point-slope, point-interecept ?

Answer 63

yes