How do you solve this math problem?

Question

Problem:
Write an equation of a line that passes through A (-1, 3) and (1, -1)

Please Help Me!

Answer 1

find the slope first, then using the slope m and one set of points, find the offset of the line, b
y=mb+x

Follow this procedure. Its easy!
http://highered.mcgraw-hill.com/sites/dl/free/007092242x/118759/MATC9_Ch10_6_KeyConcepts_1.pdf

Answer 2

First find the slope of the 2 points using the formula

slope = (y2-y1)/(x2-x1)

so given A(-1,3) and B(1,-1), the slope is

(-1-3)/(1-(-1)) = -4/2 = -2

Then find the y-intercept, b, using the formula for a straight line:

y = mx + b

b = y - mx

using either point A or B (both will yield the same answer):

b = 3 - (-2)*(-1) = 3 - 2 = 1

So the equation of the line is:

y = -2x + 1

Answer 3

There are several ways. Iíi show you one:
Find the slope =(y2-y1)/(x2-x1) =(-1-3)/(1-(-1))=-4/2= -2
So using y= mx+b, we get:
y = -2x +bNow use the point (1,-1) to find b
-1 -2(1) =b
b=-3
So the equation is y=-2x-3

Answer 4

the easiest way is to use point-slope form:
y - y1 = m(x - x1)

In your case, y = 3, y1 = -1, x = -1, and x1 = 1
so...
3 - (-1) = m(-1 - 1)
then solve for m
4 = (-2)m
m = -2

finally, return to point slope form and plug in "m" and this time only plug in "x1" and "y1".
so...
y - (-1) = -2(x - 1)
---then solve for y
y + 1 = -2x +2
y = -2x + 2 - 1
y = -2x + 1