SOLUTION: please explain how to do long division (b^3-27)/(b-3)= and then how do I check this

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: please explain how to do long division (b^3-27)/(b-3)= and then how do I check this      Log On


   



Question 427656: please explain how to do long division
(b^3-27)/(b-3)=
and then how do I check this

Answer by Edwin McCravy(20055) About Me  (Show Source):
You can put this solution on YOUR website!
(b³-27)/(b-3)=


Write b³ - 27 as b³ + 0b² + 0b - 27 

Write this:

                        
b - 3)b³ + 0b² + 0b - 27
      
b³ divided by b give b²

     
b - 3)b³ + 0b² + 0b - 27
     
b² times -3 gives -3b

     
b - 3)b³ + 0b² + 0b - 27
         - 3b²

b² times b gives b³

     
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²

Draw a line:

     
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²

Subtract b³ - b³, that gives 0 so we don't write anything
under that.  then 0b² minus -3b² is really 0b²+3b² or 3b²

     
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b²

Bring down the + 0b

     
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b

3b² divided by b give 3b

            b² + 3b     
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b

3b times -3 gives -9b

            b² + 3b     
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b
               - 9b

3b times b gives 3b²

            b² + 3b     
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b
           3b² - 9b

Draw a line:

            b² + 3b     
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b
           3b² - 9b

Subtract 3b² - 3b², that gives 0 so we don't write anything
under that.  then 0b minus -9b is really 0b+9b or 9b

            b² + 3b     
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b
           3b² - 9b
                 9b

Bring down the - 27

            b² + 3b     
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b
           3b² - 9b
                 9b - 27

9b divided by b give 9

            b² + 3b + 9
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b
           3b² - 9b
                 9b - 27
 
9 times -3 gives -27

            b² + 3b + 9
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b
           3b² - 9b
                 9b - 27
                    - 27

9 times b gives 9b

            b² + 3b + 9
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b
           3b² - 9b
                 9b - 27
                 9b - 27

Draw a line:

            b² + 3b + 9
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b
           3b² - 9b
                 9b - 27
                 9b - 27

Subtract 9b - 9b, that gives 0 so we don't write anything
under that.  then -27 minus -27 is really -27+27 or 0, so
the remainder is 0:

            b² + 3b + 9
b - 3)b³ + 0b² + 0b - 27
      b³ - 3b²
           3b² + 0b
           3b² - 9b
                 9b - 27
                 9b - 27
                       0

That's it.  The answer, or quotient, is b² + 3b + 9

Edwin