What is the equation of the line passing through (91,-41)(91,41) and (-25,7)(25,7)?

1 Answer
Mar 15, 2017

(y + color(red)(41)) = color(blue)(-12/29)(x - color(red)(91))(y+41)=1229(x91)

Or

(y - color(red)(7)) = color(blue)(-12/29)(x + color(red)(25))(y7)=1229(x+25)

Explanation:

First, we must determine the slope of the line passing through these two points. The slope can be found by using the formula: m = (color(red)(y_2) - color(blue)(y_1))/(color(red)(x_2) - color(blue)(x_1))m=y2y1x2x1

Where mm is the slope and (color(blue)(x_1, y_1)x1,y1) and (color(red)(x_2, y_2)x2,y2) are the two points on the line.

Substituting the values from the points in the problem gives:

m = (color(red)(7) - color(blue)(-41))/(color(red)(-25) - color(blue)(91)) = (color(red)(7) + color(blue)(41))/(color(red)(-25) - color(blue)(91)) = 48/(-116) = (4 xx 12)/(4 xx 29) = (color(red)(cancel(color(black)(4))) xx 12)/(color(red)(cancel(color(black)(4))) xx -29)

m = -12/29

Now, use the point-slope formula to find an equation for the line passing through the two points. The point-slope formula states: (y - color(red)(y_1)) = color(blue)(m)(x - color(red)(x_1))

Where color(blue)(m) is the slope and color(red)(((x_1, y_1))) is a point the line passes through.

Substituting the slope we calculated and the first point gives:

(y - color(red)(-41)) = color(blue)(-12/29)(x - color(red)(91))

(y + color(red)(41)) = color(blue)(-12/29)(x - color(red)(91))

We can also substitute the slope we calculated and the second point giving:

(y - color(red)(7)) = color(blue)(-12/29)(x - color(red)(-25))

(y - color(red)(7)) = color(blue)(-12/29)(x + color(red)(25))