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Solution - Simplification or other simple results

5x34
5x^3-4

Step by Step Solution

Step  1  :

Equation at the end of step  1  :

  (5x2 • x) -  4

Step  2  :

Trying to factor as a Difference of Cubes:

 2.1      Factoring:  5x3-4 

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 :  5  is not a cube !!

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

Polynomial Roots Calculator :

 2.2    Find roots (zeroes) of :       F(x) = 5x3-4
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  5  and the Trailing Constant is  -4.

 
The factor(s) are:

of the Leading Coefficient :  1,5
 
of the Trailing Constant :  1 ,2 ,4

 
Let us test ....

  P  Q  P/Q  F(P/Q)   Divisor
     -1     1      -1.00      -9.00   
     -1     5      -0.20      -4.04   
     -2     1      -2.00      -44.00   
     -2     5      -0.40      -4.32   
     -4     1      -4.00      -324.00   
     -4     5      -0.80      -6.56   
     1     1      1.00      1.00   
     1     5      0.20      -3.96   
     2     1      2.00      36.00   
     2     5      0.40      -3.68   
     4     1      4.00      316.00   
     4     5      0.80      -1.44   


Polynomial Roots Calculator found no rational roots

Final result :

  5x3 - 4

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