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Solution - Linear equations with one unknown

x=root[3]105=4.7177
x=root[3]{105}=4.7177

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 :

                     x^3-(105)=0 

Step by step solution :

Step  1  :

Trying to factor as a Difference of Cubes:

 1.1      Factoring:  x3-105 

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 :  105  is not a cube !!
Ruling : Binomial can not be factored as the difference of two perfect cubes

Polynomial Roots Calculator :

 1.2    Find roots (zeroes) of :       F(x) = x3-105
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  -105.

 
The factor(s) are:

of the Leading Coefficient :  1
 
of the Trailing Constant :  1 ,3 ,5 ,7 ,15 ,21 ,35 ,105

 
Let us test ....

  P  Q  P/Q  F(P/Q)   Divisor
     -1     1      -1.00      -106.00   
     -3     1      -3.00      -132.00   
     -5     1      -5.00      -230.00   
     -7     1      -7.00      -448.00   
     -15     1     -15.00     -3480.00   
     -21     1     -21.00     -9366.00   
     -35     1     -35.00     -42980.00   
     -105     1     -105.00     -1157730.00   
     1     1      1.00      -104.00   
     3     1      3.00      -78.00   
     5     1      5.00      20.00   
     7     1      7.00      238.00   
     15     1      15.00      3270.00   
     21     1      21.00      9156.00   
     35     1      35.00     42770.00   
     105     1     105.00     1157520.00   


Polynomial Roots Calculator found no rational roots

Equation at the end of step  1  :

  x3 - 105  = 0 

Step  2  :

Solving a Single Variable Equation :

 2.1      Solve  :    x3-105 = 0 

 
Add  105  to both sides of the equation : 
 
                     x3 = 105
When two things are equal, their cube roots are equal. Taking the cube root of the two sides of the equation we get:  
 
                     x  =  ∛ 105  

 
The equation has one real solution
This solution is  x = ∛105 = 4.7177

One solution was found :

                   x = ∛105 = 4.7177

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