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Pre algebra hw helllllllpppp!!! ASAP?

+1 vote
Write the equation of the line that passes through each pair of points in slope intercept form.
(-1,1) and (3,-3)
I got the answer which is: y=-x but I don't know how I got that answer
asked Feb 9, 2013 in PRE-ALGEBRA by skylar Apprentice

2 Answers

0 votes

Given the points are (-1, 1) and (3, -3)

The equation of the line that passes through each pair of points in slope intercept form (y-y₁)=m(x-x₁)

Where m = (y₂ - y₁)/(x₂ - x₁)

So, m = (-3-1)/(3-(-1)) = -4/4 = -1.

(y - 1) = -1(x - (-1))

y-1 = -1(x+1)

Distribute terms using distributive property:  a( b + c) = ab + ac

y -1 = -x -1

Add 1 to each side.

y = -x

Therefore the slope-intercept form is y = -x.

answered Feb 11, 2013 by britally Apprentice
0 votes

Slope - intercept form line equation is y = mx + b, where m is slope and b is y - intercept.

Let the points are (x₁, y₁) = (- 1, 1) and (x₂, y₂) = (3, - 3).

Slope (m) = [(y₂ - y₁)/(x₂ -x₁)]

m = [(- 3 - 1)/(3 - (- 1))]

m  = [- 4/(3 + 1)]

m = - 4/4

m = - 1.

Now, the line equation is y = - x + b.

Find the y - intercept by substituting any point in the line equation say (x, y) = (- 1, 1).

1 = (- 1)(- 1) + b

b = 1 - 1

b = 0.

The line equation in slope - intercept - form is y = (- 1)x + (0).

answered Jul 4, 2014 by lilly Expert

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