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Solution - Linear equations with one unknown

x=root[3]71=4.1408
x=root[3]{71}=4.1408

Step by Step Solution

Rearrange:

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

                     355-(5*x^3)=0 

Step by step solution :

Step  1  :

Equation at the end of step  1  :

  355 -  5x3  = 0 

Step  2  :

Step  3  :

Pulling out like terms :

 3.1     Pull out like factors :

   355 - 5x3  =   -5 • (x3 - 71) 

Trying to factor as a Difference of Cubes:

 3.2      Factoring:  x3 - 71 

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 :  71  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) = x3 - 71
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  1  and the Trailing Constant is  -71.

 
The factor(s) are:

of the Leading Coefficient :  1
 
of the Trailing Constant :  1 ,71

 
Let us test ....

  P  Q  P/Q  F(P/Q)   Divisor
     -1     1      -1.00      -72.00   
     -71     1     -71.00     -357982.00   
     1     1      1.00      -70.00   
     71     1      71.00     357840.00   


Polynomial Roots Calculator found no rational roots

Equation at the end of step  3  :

  -5 • (x3 - 71)  = 0 

Step  4  :

Equations which are never true :

 4.1      Solve :    -5   =  0

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

Solving a Single Variable Equation :

 4.2      Solve  :    x3-71 = 0 

 
Add  71  to both sides of the equation : 
 
                     x3 = 71
When two things are equal, their cube roots are equal. Taking the cube root of the two sides of the equation we get:  
 
                     x  =  ∛ 71  

 
The equation has one real solution
This solution is  x = ∛71 = 4.1408

One solution was found :

                   x = ∛71 = 4.1408

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