How do you write the equation in point slope form given (-3, -2), (2,-1)?

1 Answer
Jan 13, 2017

#(y + color(red)(2)) = color(blue)(1/5)(x + color(red)(3))#

or

#(y + color(red)(1)) = color(blue)(1/5)(x - color(red)(2))#

Explanation:

First, we need to determine the slope.

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))#

Where #m# is the slope and (#color(blue)(x_1, y_1)#) and (#color(red)(x_2, y_2)#) are the two points on the line.

Substituting our two points gives:

#m = (color(red)(-1) - color(blue)(-2))/(color(red)(2) - color(blue)(-3))#

#m = (color(red)(-1) + color(blue)(2))/(color(red)(2) + color(blue)(3))#

#m = 1/5#

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 values from the two points given in the problem and the slope we calculated results in:

#(y - color(red)(-2)) = color(blue)(1/5)(x - color(red)(-3))#

#(y + color(red)(2)) = color(blue)(1/5)(x + color(red)(3))#

or

#(y - color(red)(-1)) = color(blue)(1/5)(x - color(red)(2))#

#(y + color(red)(1)) = color(blue)(1/5)(x - color(red)(2))#