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Solution - Reducing fractions to their lowest terms

(4x3-10x2+7)/(x4+3x3-25x2-28)
(4x^3-10x^2+7)/(x^4+3x^3-25x^2-28)

Step by Step Solution

Step  1  :

            28
 Simplify   ——
            x2

Equation at the end of step  1  :

         7          28
  (((x+————)+3x)-10)——)-25)
       (x2)((((x^2)+x2

Step  2  :

Rewriting the whole as an Equivalent Fraction :

 2.1   Subtracting a fraction from a whole

Rewrite the whole as a fraction using  x2  as the denominator :

                x2 + 3x     (x2 + 3x) • x2
     x2 + 3x =  ———————  =  ——————————————
                   1              x2      

Equivalent fraction : The fraction thus generated looks different but has the same value as the whole

Common denominator : The equivalent fraction and the other fraction involved in the calculation share the same denominator

Step  3  :

Pulling out like terms :

 3.1     Pull out like factors :

   x2 + 3x  =   x • (x + 3) 

Adding fractions that have a common denominator :

 3.2       Adding up the two equivalent fractions
Add the two equivalent fractions which now have a common denominator

Combine the numerators together, put the sum or difference over the common denominator then reduce to lowest terms if possible:

 x • (x+3) • x2 - (28)     x4 + 3x3 - 28
 —————————————————————  =  —————————————
          x2                    x2      

Equation at the end of step  3  :

         7          (x4+3x3-28)
  (((x+————)+3x)-10)———————————-25)
       (x2)(            x2     

Step  4  :

Rewriting the whole as an Equivalent Fraction :

 4.1   Subtracting a whole from a fraction

Rewrite the whole as a fraction using  x2  as the denominator :

          25     25 • x2
    25 =  ——  =  ———————
          1        x2   

Polynomial Roots Calculator :

 4.2    Find roots (zeroes) of :       F(x) = x4 + 3x3 - 28
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  -28.

 
The factor(s) are:

of the Leading Coefficient :  1
 
of the Trailing Constant :  1 ,2 ,4 ,7 ,14 ,28

 
Let us test ....

  P  Q  P/Q  F(P/Q)   Divisor
     -1     1      -1.00      -30.00   
     -2     1      -2.00      -36.00   
     -4     1      -4.00      36.00   
     -7     1      -7.00      1344.00   
     -14     1     -14.00     30156.00   
     -28     1     -28.00     548772.00   
     1     1      1.00      -24.00   
     2     1      2.00      12.00   
     4     1      4.00      420.00   
     7     1      7.00      3402.00   
     14     1      14.00     46620.00   
     28     1      28.00     680484.00   


Polynomial Roots Calculator found no rational roots

Adding fractions that have a common denominator :

 4.3       Adding up the two equivalent fractions

 (x4+3x3-28) - (25 • x2)     x4 + 3x3 - 25x2 - 28
 ———————————————————————  =  ————————————————————
           x2                         x2         

Equation at the end of step  4  :

         7          (x4+3x3-25x2-28)
  (((x+————)+3x)-10)————————————————
       (x2)                x2       

Step  5  :

7 Simplify —— x2

Equation at the end of step  5  :

   7                (x4 + 3x3 - 25x2 - 28)
  ——) + 3x) - 10) ÷ ——————————————————————
  x2                          x2          

Step  6  :

Rewriting the whole as an Equivalent Fraction :

 6.1   Adding a fraction to a whole

Rewrite the whole as a fraction using  x2  as the denominator :

          x     x • x2
     x =  —  =  ——————
          1       x2  

Adding fractions that have a common denominator :

 6.2       Adding up the two equivalent fractions

 x • x2 + 7     x3 + 7
 ——————————  =  ——————
     x2           x2  

Equation at the end of step  6  :

  (x3 + 7)               (x4 + 3x3 - 25x2 - 28)
  ———————— + 3x) - 10) ÷ ——————————————————————
     x2                            x2          

Step  7  :

Rewriting the whole as an Equivalent Fraction :

 7.1   Adding a whole to a fraction

Rewrite the whole as a fraction using  x2  as the denominator :

          3x     3x • x2
    3x =  ——  =  ———————
          1        x2   

Trying to factor as a Sum of Cubes :

 7.2      Factoring:  x3 + 7 

Theory : A sum 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 :  7  is not a cube !!
Ruling : Binomial can not be factored as the difference of two perfect cubes

Polynomial Roots Calculator :

 7.3    Find roots (zeroes) of :       F(x) = x3 + 7

     See theory in step 4.2
In this case, the Leading Coefficient is  1  and the Trailing Constant is  7.

 
The factor(s) are:

of the Leading Coefficient :  1
 
of the Trailing Constant :  1 ,7

 
Let us test ....

  P  Q  P/Q  F(P/Q)   Divisor
     -1     1      -1.00      6.00   
     -7     1      -7.00      -336.00   
     1     1      1.00      8.00   
     7     1      7.00      350.00   


Polynomial Roots Calculator found no rational roots

Adding fractions that have a common denominator :

 7.4       Adding up the two equivalent fractions

 (x3+7) + 3x • x2     4x3 + 7
 ————————————————  =  ———————
        x2              x2   

Equation at the end of step  7  :

  (4x3 + 7)         (x4 + 3x3 - 25x2 - 28)
  ————————— - 10) ÷ ——————————————————————
     x2                       x2          

Step  8  :

Rewriting the whole as an Equivalent Fraction :

 8.1   Subtracting a whole from a fraction

Rewrite the whole as a fraction using  x2  as the denominator :

          10     10 • x2
    10 =  ——  =  ———————
          1        x2   

Trying to factor as a Sum of Cubes :

 8.2      Factoring:  4x3 + 7 

Check :  4  is not a cube !!

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

Polynomial Roots Calculator :

 8.3    Find roots (zeroes) of :       F(x) = 4x3 + 7

     See theory in step 4.2
In this case, the Leading Coefficient is  4  and the Trailing Constant is  7.

 
The factor(s) are:

of the Leading Coefficient :  1,2 ,4
 
of the Trailing Constant :  1 ,7

 
Let us test ....

  P  Q  P/Q  F(P/Q)   Divisor
     -1     1      -1.00      3.00   
     -1     2      -0.50      6.50   
     -1     4      -0.25      6.94   
     -7     1      -7.00     -1365.00   
     -7     2      -3.50      -164.50   
     -7     4      -1.75      -14.44   
     1     1      1.00      11.00   
     1     2      0.50      7.50   
     1     4      0.25      7.06   
     7     1      7.00      1379.00   
     7     2      3.50      178.50   
     7     4      1.75      28.44   


Polynomial Roots Calculator found no rational roots

Adding fractions that have a common denominator :

 8.4       Adding up the two equivalent fractions

 (4x3+7) - (10 • x2)     4x3 - 10x2 + 7
 ———————————————————  =  ——————————————
         x2                    x2      

Equation at the end of step  8  :

  (4x3 - 10x2 + 7)   (x4 + 3x3 - 25x2 - 28)
  ———————————————— ÷ ——————————————————————
         x2                    x2          

Step  9  :

         4x3-10x2+7      x4+3x3-25x2-28
 Divide  ——————————  by  ——————————————
             x2                x2      


 9.1    Dividing fractions

To divide fractions, write the divison as multiplication by the reciprocal of the divisor :

4x3 - 10x2 + 7     x4 + 3x3 - 25x2 - 28       4x3 - 10x2 + 7               x2          
——————————————  ÷  ————————————————————   =   ——————————————  •  ——————————————————————
      x2                    x2                      x2           (x4 + 3x3 - 25x2 - 28)

Checking for a perfect cube :

 9.2    x4 + 3x3 - 25x2 - 28  is not a perfect cube

Trying to factor by pulling out :

 9.3      Factoring:  x4 + 3x3 - 25x2 - 28 

Thoughtfully split the expression at hand into groups, each group having two terms :

Group 1:  -25x2 - 28 
Group 2:  x4 + 3x3 

Pull out from each group separately :

Group 1:   (25x2 + 28) • (-1)
Group 2:   (x + 3) • (x3)

Bad news !! Factoring by pulling out fails :

The groups have no common factor and can not be added up to form a multiplication.

Polynomial Roots Calculator :

 9.4    Find roots (zeroes) of :       F(x) = 4x3 - 10x2 + 7

     See theory in step 4.2
In this case, the Leading Coefficient is  4  and the Trailing Constant is  7.

 
The factor(s) are:

of the Leading Coefficient :  1,2 ,4
 
of the Trailing Constant :  1 ,7

 
Let us test ....

  P  Q  P/Q  F(P/Q)   Divisor
     -1     1      -1.00      -7.00   
     -1     2      -0.50      4.00   
     -1     4      -0.25      6.31   
     -7     1      -7.00     -1855.00   
     -7     2      -3.50      -287.00   
     -7     4      -1.75      -45.06   
     1     1      1.00      1.00   
     1     2      0.50      5.00   
     1     4      0.25      6.44   
     7     1      7.00      889.00   
     7     2      3.50      56.00   
     7     4      1.75      -2.19   


Polynomial Roots Calculator found no rational roots

Polynomial Roots Calculator :

 9.5    Find roots (zeroes) of :       F(x) = x4 + 3x3 - 25x2 - 28

     See theory in step 4.2
In this case, the Leading Coefficient is  1  and the Trailing Constant is  -28.

 
The factor(s) are:

of the Leading Coefficient :  1
 
of the Trailing Constant :  1 ,2 ,4 ,7 ,14 ,28

 
Let us test ....

  P  Q  P/Q  F(P/Q)   Divisor
     -1     1      -1.00      -55.00   
     -2     1      -2.00      -136.00   
     -4     1      -4.00      -364.00   
     -7     1      -7.00      119.00   
     -14     1     -14.00     25256.00   
     -28     1     -28.00     529172.00   
     1     1      1.00      -49.00   
     2     1      2.00      -88.00   
     4     1      4.00      20.00   
     7     1      7.00      2177.00   
     14     1      14.00     41720.00   
     28     1      28.00     660884.00   


Polynomial Roots Calculator found no rational roots

Final result :

     4x3 - 10x2 + 7   
  ————————————————————
  x4 + 3x3 - 25x2 - 28

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