Solution - Factoring binomials using the difference of squares

Step by step solution :

Step  1  :

Equation at the end of step  1  :

  81 -  22b2  = 0 

Step  2  :

Trying to factor as a Difference of Squares :

 2.1      Factoring:  81-4b² 

Theory : A difference of two perfect squares,  A² - B²  can be factored into  (A+B) • (A-B)

Proof :  (A+B) • (A-B) =
         A² - AB + BA - B² =
         A² - AB + AB - B² =
         A² - B²

Note :  AB = BA is the commutative property of multiplication.

Note :  - AB + AB equals zero and is therefore eliminated from the expression.

Check :  81  is the square of  9 
Check : 4 is the square of 2
Check :  b²  is the square of  b¹ 

Factorization is :       (9 + 2b)  •  (9 - 2b) 

Equation at the end of step  2  :

  (2b + 9) • (9 - 2b)  = 0 

Step  3  :

Theory - Roots of a product :

 3.1    A product of several terms equals zero. 

 When a product of two or more terms equals zero, then at least one of the terms must be zero. 

 We shall now solve each term = 0 separately 

 In other words, we are going to solve as many equations as there are terms in the product 

 Any solution of term = 0 solves product = 0 as well.

Solving a Single Variable Equation :

 3.2      Solve  :    2b+9 = 0 

 Subtract  9  from both sides of the equation : 
                      2b = -9
Divide both sides of the equation by 2:
                     b = -9/2 = -4.500

Solving a Single Variable Equation :

 3.3      Solve  :    -2b+9 = 0 

 Subtract  9  from both sides of the equation : 
                      -2b = -9
Multiply both sides of the equation by (-1) :  2b = 9


Divide both sides of the equation by 2:
                     b = 9/2 = 4.500

Two solutions were found :

1.  b = 9/2 = 4.500
   
2.  b = -9/2 = -4.500