Question

what is the equation of a line that passes through the point (-2,1)?

Answer 1

you cant get a line equation only with one point

Answer 2

y=mx+b is a line
we aren't given any info about the slope
so i guess we can use any slope we want but it does the equation not a equation
so m is the slope
we know a point on the line so we can find b (the yintercept)
1=-2m+b
1+2m=b
1+2m is the y-intercept
so the equation of the line is y=mx+(1+2m)

Answer 3

you need another point or a slope

Answer 4

the multiple choice answers for this problem are
A) y=-x + 1
B) y=-x -2
C) y=1-x
Dy=2-x
so any ideas on how to get on of the answers?
by the way myinaya you are good at explaining things.

Answer 5

so i guess it is looking for a equation
so we have y=mx+(1+2m)
lets see which of the above lines fit this
they all have slope -1 right?
m=-1 then
so
y=-1x+(1+2(-1))
y=-x+(1-2)
y=-x-1

Answer 6

i don't see this choice

Answer 7

oh yah that is a choice actually. sorry i wrote it wrong!

Answer 8

good lol i was fixing to say none of these lol

Answer 9

i go to bed gl with your math problems :)

Answer 10

wait i have a question... how ddo you know that they have a -1 slope

Answer 11

one more thing you could went through all of them
in plug in x=-2 and y=1
and if you got the same thing on both sides then that is the line you are looking for
like for instance
A is y=-x+1
A is wrong since 1 does not equal 3
B is y=-x-2
B is wrong since 1 does not equal 0
C is y=1-x
C is wrong since 1 does not equal 3
D is y=2-x
D is wrong since 1 does not equal 4
also A and C are the same equation
i bet it was one those you wrote wrong

Answer 12

all them are pretty much in y=mx+b form
the coeifficient of x is the slope
they all have -1 in front of x
we can only determine the slope if the line is written in y=mx+b form by the way not
ax+by=c
it has to be y=mx+b

Answer 13

y=-x-1 is the line we found to be the right one
(-2,1)
x=-2 and y=1
1=-(-2)-1=1
since we have the same thing on both sides this is the line that (-2,1) is on

Answer 14

one last question and then you can go to bed....
How do you solve ....what is the equation of the line that passes through points (7,-4) and (-3,5)?

Answer 15

a line has the form y=mx+b
so we need to know two things: slope=m and the y-intercept=b
so we can find the slope because we are given two points
m=slope=change of y/change of x=(5-(-4))/(-3-7)=9/(-10)=-9/10
so we know m so can fill one blank
y=-9/10*x+b
we know a point on the line (you can use either one-you will get the same thing)
say we choose (-3,5)
x=-3
y=5
so we only have one unknown in the equation y=-9/10*x+b since we know a point
so we have 5=-9/10*(-3)+b
5=27/10+b
5-27/10=b
50/10-27/10=b (found common denominator)
23/10=b
so we know both m and b now so we can now write our equation
y=-9/10*x+23/10

Answer 16

you can also write the line in general form ax+by=c
multiply 10 on bot sides
10y=-9x+23
add 9x on both sides
10y+9x=23
9x+10y=23

Answer 17

good?

Answer 18

goodnight?

Answer 19

sory my computer froze...
the answer choices are
y+4=-9/10(x-7)
or
y-4 = -9/10(x + 7)
which one?

Answer 20

ok so we see the form it is written in
y-y0=m(x-x0)
(x0,y0)=(7,-4)
m=-9/10
so
y-(-4)=-9/10(x-7)
y+4=-9/10(x-7)

Answer 21

the first one

Answer 22

thx.goodnight

Answer 23

(x0,y0) is a point on the line and (7,-4) was the point they used so thats why i chose that point instead of the other but it doesn't matter what point you do use because you can manipulate both to show that they are the same

Answer 24

goodnight :)