Write an equation in slope-intercept form of the line that passes trough (6,-1) and (3,-7

Answer 1

Hi Joham. First find the slope: m = (-7 - -1)/(3 - 6) = -6/-3 = 2 Be careful with signs!

Now we have the slope and 2 points so use point slope form with one of the points

y - y1 = m(x - x1)

y - (-1) = 2(x - 6)

y + 1 = 2x - 12 Now solve for y

y = 2x - 13 (slope intercept form)

You can check your answer by plugging in the x's and seeing that you get the right y's

y = 2 * 6 - 13 = 12 - 13 = -1

y = 2*3 - 13 = 6 -13 = -7 so all is good. Yeah!

Answer 2

SLOPE

A quick way to find the slope is to compare the y-values and the x-values.

- For the y's, from -1 to -7, that's -6

- For the x's, from 6 to 3, that's -3

So the slope is -6/-3, which is equal to just 2 (division).

(This is a shortcut of the slope formula. If you must use the formula instead, do that, using (6, -1) as (x1, y1) and (3, -7) as (x2, y2))

Y-INTERCEPT

To find the y-intercept, take either one of the points and the slope, and plug into y = mx + b, then solve for b. Let's take the first point

(6, -1)

-1 = 2(6) + b

-1 = 12 + b

(Minus 12 on both sides)

-13 = b

(An alternative would've been using point-slope form)

So the equation of the line is: y = 2x - 13

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