Free Algebra
Tutorials!
 
Try the Free Math Solver or Scroll down to Tutorials!

 

 

 

 

 

 

 

 
 
 
 
 
 
 
 
 

 

 

 
 
 
 
 
 
 
 
 

Please use this form if you would like
to have this math solver on your website,
free of charge.


Multiplying Polynomials

What to Do How to Do It
1. The most basic property of algebra necessary to multiplying polynomials is the distributive property.   A(B + C) = AB + AC
2. This can be extended to several terms inside the parenthesis: (The three dots ... mean and so on in the pattern.)   → A(B + C + D + ... )

   = AB + AC + AD + ...

3. Both multiplicands may be binomials, in which case the property is usually referred to as the “double distributive property”.   (A + B)(C + D)

  = A(C + D) + B(C + D)

  = AC + AD + BC + BD

4. Consider the following examples:  
a) 2(x + 3) =   2(x + 3)

  = 2x + 2·3

  = 2x + 6

b) 3x(x-1) =   3x(x - 1)

  = 3x·x + 3x·(-1)

  = 3x2 - 3x

c) - 5(x2 + 2x - 3) =   - 5(x2 + 2x - 3)

  = (- 5)(x2) + (- 5)(2x) + (- 5)(- 3)

  = - 5x2 - 10x + 15

d) (x + a)(y + b) =   → (x + a)(y + b)

  = x(y + b) + a(y + b)

  = xy + xb + ay + ab

e) (x + 2)(2x + 3) =

With practice we can do the second line in our head and go directly to the third line.

  (x + 2) (2x + 3)

  = x (2x + 3) + 2(2x + 3)

  = x·2x + x·3 + 2·2x + 2·3

  = 2x2 + 3x + 4x + 6

  = 2x2 + 7x + 6

 

f) (2x + 3)(2x + 3) =

Later, skip this second line and →

go directly to this third line. →

  (2x + 3) (2x + 3)

  = 2x·2x + 2x·3 + 3·2x + 3·3

  = 4x2 + 6x + 6x + 9    

  = 4x2 + 12x + 9

g) (2x + 3)(2x - 3) =

Note the “equal and opposites” →

cancel out here.

  (2x + 3) (2x - 3)

  = 2x·2x + 2x·(- 3) + 3·2x + 3·(- 3)

  = 4x2 - 6x + 6x - 9

  = 4x2 - 9

     

 
All Right Reserved. Copyright 2005-2024