Determining the Linear Equation

Question

Given the points:

P(–1, 4) and Q(3, –8)

Questions:

1. What is the slope of the line passing through points P and Q?
2. Based on your answer, write the equation of the line in slope-intercept form (y = mx + b).

Use the slope formula and plug in the coordinates carefully. Show your work for full credit.

Answer 1

(-1,4), (3,-8)

m=-3 = rise over run

y=-3x +1

Answer 2

Hi Lorde,

Remember the slope formula is m = (y2 - y1)/(x2-x1)

so slope m = (-8 - 4)/(3- -1) = (-12)/4 = -3

The slope of the line passing through P and Q is -3

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y = mx + b

You know m, you can plug P or Q's coordinates for x and y (let's use Q):

-8 = -3(3) + b

-8 = -9+b

1 = b

So the slope-intercept equation of the line is y = -3x +1