Slope Intercept

Question

x+9y=-18 

 

Place in Slope Intercept Form

Answer 1

If you know how to solve equations, you know how to do this!

 

Remember:  

 

Standard Form of a linear equation:              Ax + By = C

 

Slope-Intercept Form of a linear equation:     y  =  mx + b

 

You have been given the equation in standard form.  To change it to the slope-intercept form you need to isolate y.  (That is, you need to solve for y, so y is all by itself on one side of the equation.)  

 

   x   +   9y   =   -18

  -x                     -x                    subtract x from both sides

------------------------------

             9y   =   -x  -  18

 

           9y/9   =   (-x  -  18)/9       divide both sides by 9

 

              y     =   (-1/9)x  -  2      This is the equation in slope-intercept form!

 

You may want to check that this is correct by picking a few x values and making sure you get the same y using both forms of the equation.

 

 

Answer 2

Slope-intercept form of the equation of a line looks like:    y=mb+b     where m=slope; b=y-intercept

 

Isolate y:

   x+9y=-18

       9y=-x-18        [subtract x from both sides]

       y = (-1/9)x - 2         [divide both sides by 9]

 

Now, if you can remember a couple y=mx+b, then you should remember this also:

  The equation of a line in Standard Form looks like:    Ax + By = C

     [now, convert it to slope-intercept form]

        y = (-A/B)x + (C/B)         the slope m=(-A/B);  b=(C/B)

So,

  to convert:          (1)x + (9)y = (-18)              [this is Ax + By = C]

   the result is:      y = (-1/9)x + (-18)/(9)        [this is y = (-A/B)x + (C/B) ]

                           y = (-1/9) - 2