Solution - Nonlinear equations

Rearrange:

Rearrange the equation by subtracting what is to the right of the equal sign from both sides of the equation :

                     2*x^2-3-(18)=0 

Step by step solution :

Step  1  :

Equation at the end of step  1  :

  (2x2 -  3) -  18  = 0 

Step  2  :

Trying to factor as a Difference of Squares :

 2.1      Factoring:  2x²-21 

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 :  2  is not a square !!

Ruling : Binomial can not be factored as the
difference of two perfect squares

Equation at the end of step  2  :

  2x2 - 21  = 0 

Step  3  :

Solving a Single Variable Equation :

 3.1      Solve  :    2x²-21 = 0 

 Add  21  to both sides of the equation : 
                      2x² = 21
Divide both sides of the equation by 2:
                     x² = 21/2 = 10.500
 
 When two things are equal, their square roots are equal. Taking the square root of the two sides of the equation we get:  
                      x  =  ± √ 21/2  

 The equation has two real solutions  
 These solutions are  x = ±√ 10.500 = ± 3.24037  
 

Two solutions were found :