How do you write an equation in slope intercept form using the points (4,-3) , (2,3)?

1 Answer
Jan 18, 2017

Answer:

#y = -3x + 9#

Explanation:

First, we will write and equation in point-slope form and then convert to slope-intercept form.

To use the point-slope form we must first 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 the values from the points in the problem gives:

#m = (color(red)(3) - color(blue)(-3))/(color(red)(2) - color(blue)(4))#

#m = (color(red)(3) + color(blue)(3))/(color(red)(2) - color(blue)(4))#

#m = 6/-2 = -3#

We can now use this calculated slope and either point to write the equation in point-slope form.

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.

Again, substituting gives:

#(y - color(red)(-3)) = color(blue)(-3)(x - color(red)(4))#

#(y + color(red)(3)) = color(blue)(-3)(x - color(red)(4))#

We can now convert this to slope-intercept form.

The slope-intercept form of a linear equation is:

#y = color(red)(m)x + color(blue)(b)#

Where #color(red)(m)# is the slope and #color(blue)(b)# is the y-intercept value.

We can solve our equation for #y#:

#(y + color(red)(3)) = color(blue)(-3)(x - color(red)(4))#

#y + color(red)(3) = (color(blue)(-3) xx x) - (color(blue)(-3) xx color(red)(4))#

#y + 3 = -3x - (-12)#

#y + 3 = -3x + 12#

#y + 3 - color(red)(3) = -3x + 12 - color(red)(3)#

#y + 0 = -3x + 9#

#y = -3x + 9#