Solution - Nonlinear equations

Step by step solution :

Step  1  :

Equation at the end of step  1  :

  ((2•3x2) • x) -  15  = 0 
 Step  2  :
 Step  3  :

Pulling out like terms :

 3.1     Pull out like factors :

   6x³ - 15  =   3 • (2x³ - 5) 

Trying to factor as a Difference of Cubes:

 3.2      Factoring:  2x³ - 5 

Theory : A difference of two perfect cubes,  a³ - b³ can be factored into
              (a-b) • (a² +ab +b²)

Proof :  (a-b)•(a²+ab+b²) =
            a³+a²b+ab²-ba²-b²a-b³ =
            a³+(a²b-ba²)+(ab²-b²a)-b³ =
            a³+0+0-b³ =
            a³-b³

Check :  2  is not a cube !!

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

Polynomial Roots Calculator :

 3.3    Find roots (zeroes) of :       F(x) = 2x³ - 5
Polynomial Roots Calculator is a set of methods aimed at finding values of  x  for which   F(x)=0  

Rational Roots Test is one of the above mentioned tools. It would only find Rational Roots that is numbers  x  which can be expressed as the quotient of two integers

The Rational Root Theorem states that if a polynomial zeroes for a rational number  P/Q   then  P  is a factor of the Trailing Constant and  Q  is a factor of the Leading Coefficient

In this case, the Leading Coefficient is  2  and the Trailing Constant is  -5.

 The factor(s) are:

of the Leading Coefficient :  1,2
 of the Trailing Constant :  1 ,5

 Let us test ....

Polynomial Roots Calculator found no rational roots

Equation at the end of step  3  :

  3 • (2x3 - 5)  = 0 

Step  4  :

Equations which are never true :

 4.1      Solve :    3   =  0

This equation has no solution.
A a non-zero constant never equals zero.

Solving a Single Variable Equation :

 4.2      Solve  :    2x³-5 = 0 

 Add  5  to both sides of the equation : 
                      2x³ = 5
Divide both sides of the equation by 2:
                     x³ = 5/2 = 2.500
When two things are equal, their cube roots are equal. Taking the cube root of the two sides of the equation we get:  
                      x  =  ∛ 5/2  

 The equation has one real solution
This solution is  x = ∛ 2.500 = 1.35721

One solution was found :