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Solution - Finding the roots of polynomials

y=4
y=4

Step by Step Solution

Step by step solution :

Step  1  :

Polynomial Roots Calculator :

 1.1    Find roots (zeroes) of :       F(y) = y5+y-1028
Polynomial Roots Calculator is a set of methods aimed at finding values of  y  for which   F(y)=0  

Rational Roots Test is one of the above mentioned tools. It would only find Rational Roots that is numbers  y  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  -1028.

 
The factor(s) are:

of the Leading Coefficient :  1
 
of the Trailing Constant :  1 ,2 ,4 ,257 ,514 ,1028

 
Let us test ....

  P  Q  P/Q  F(P/Q)   Divisor
     -1     1      -1.00     -1030.00   
     -2     1      -2.00     -1062.00   
     -4     1      -4.00     -2056.00   
     -257     1     -257.00     -1121154894342.00   
     -514     1     -514.00     -35876956579366.00   
     -1028     1     -1028.00     -1148062610492424.00   
     1     1      1.00     -1026.00   
     2     1      2.00      -994.00   
     4     1      4.00      0.00    y-4 
     257     1     257.00     1121154892286.00   
     514     1     514.00     35876956577310.00   
     1028     1     1028.00     1148062610490368.00   


The Factor Theorem states that if P/Q is root of a polynomial then this polynomial can be divided by q*x-p Note that q and p originate from P/Q reduced to its lowest terms

In our case this means that
   y5+y-1028 
can be divided with  y-4 

Polynomial Long Division :

 1.2    Polynomial Long Division
Dividing :  y5+y-1028 
                              ("Dividend")
By         :    y-4    ("Divisor")

dividend  y5       + y - 1028 
- divisor * y4   y5 - 4y4         
remainder    4y4     + y - 1028 
- divisor * 4y3     4y4 - 16y3       
remainder      16y3   + y - 1028 
- divisor * 16y2       16y3 - 64y2     
remainder        64y2 + y - 1028 
- divisor * 64y1         64y2 - 256y   
remainder          257y - 1028 
- divisor * 257y0           257y - 1028 
remainder           0

Quotient :  y4+4y3+16y2+64y+257  Remainder:  0 

Polynomial Roots Calculator :

 1.3    Find roots (zeroes) of :       F(y) = y4+4y3+16y2+64y+257

     See theory in step 1.1
In this case, the Leading Coefficient is  1  and the Trailing Constant is  257.

 
The factor(s) are:

of the Leading Coefficient :  1
 
of the Trailing Constant :  1 ,257

 
Let us test ....

  P  Q  P/Q  F(P/Q)   Divisor
     -1     1      -1.00      206.00   
     -257     1     -257.00     4295612622.00   
     1     1      1.00      342.00   
     257     1     257.00     4431442262.00   


Polynomial Roots Calculator found no rational roots

Equation at the end of step  1  :

  (y4 + 4y3 + 16y2 + 64y + 257) • (y - 4)  = 0 

Step  2  :

Theory - Roots of a product :

 2.1    A product of several terms equals zero. 

 
When a product of two or more terms equals zero, then at least one of the terms must be zero. 

 
We shall now solve each term = 0 separately 

 
In other words, we are going to solve as many equations as there are terms in the product 

 
Any solution of term = 0 solves product = 0 as well.

Quartic Equations :

 2.2     Solve   y4+4y3+16y2+64y+257 = 0

In search of an interavl at which the above polynomial changes sign, from negative to positive or the other wayaround.

Method of search: Calculate polynomial values for all integer points between y=-20 and y=+20

No interval at which a change of sign occures has been found. Consequently, Bisection Approximation can not be used. As this is a polynomial of an even degree it may not even have any real (as opposed to imaginary) roots

Solving a Single Variable Equation :

 2.3      Solve  :    y-4 = 0 

 
Add  4  to both sides of the equation : 
 
                     y = 4

One solution was found :

                   y = 4

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