SOLUTION: Solve 6x⁴ - 35x³ + 62x² - 35x + 6 = 0

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Question 1131704: Solve 6x⁴ - 35x³ + 62x² - 35x + 6 = 0
Found 4 solutions by rothauserc, MathLover1, ikleyn, MathTherapy:
Answer by rothauserc(4718)   (Show Source): You can put this solution on YOUR website!
6x^4 - 35x^3 + 62x^2 - 35x + 6 = 0
:
check for the factors of 6(this is the constant and also the leading coefficient in the above equation)
:
use the Rational Zeros Theorem
:
factors for 6 are 1, 2, 3, 6
:
the possible zeros are
:
(+ or - 1, 2, 3, 6)/(1, 2, 3, 6) = + or - 1, 2, 3, 6, 1/2, 1, 3/2, 3, 1/3, 2/3, 1, 2, 1/6, 1/3, 1/2, 1 =
:
-6, -3, -2, -3/2, -1, -1/2, -2/3, -1/3, -1/6, 1/6, 1/3, 2/3, 1/2, 1, 3/2, 2, 3, 6
:
look at the graph to see if we can eliminate any of the possible zeros
:

:
from the graph we see that there are no negative roots and 4 positive roots
:
we can eliminate 1/6, 2/3, 1, 3/2, 6
:
*******************************************************
the roots are 1/3, 1/2, 2, 3
:
to check this substitute for x in the equation
*******************************************************

Answer by MathLover1(20850)   (Show Source): You can put this solution on YOUR website!

Solve
....factor completely
write as
and as

...group












solutions:





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Answer by ikleyn(52863)   (Show Source): You can put this solution on YOUR website!
.

            This equation of the degree  4  is VERY SPECIAL.
            It relates to the class of so named  palindromic  equations  of the degree  4,  which means that its coefficients
            form a palindromic sequence.

            See this Wikipedia article https://en.wikipedia.org/wiki/Reciprocal_polynomial#Palindromic_polynomial

            There is a  SPECIAL  PROCEDURE  in algebra to solve such equations.  It is presented below.


 = 0      (1)


It follows from the equation that x= 0 IS NOT the root.
So, we can divide both sides by    without loosing the roots. In this way, you will get an equivalent equation


 = 0.


Group and re-write it equivalently in the form


 -  + 50 = 0,    or


 -  + 50 = 0.     (2)


Introduce new variable  u =  + .  Then equation (2) takes a form


 = 0.


Solve this quadratic equation using the quadratic formula


 =  = .


The two roots are  

     =  =  =  =   and

     =  =  =  = .


Now, to find x,  we need to solve two equations

    a)   +  =    and  b)   +  = .



Case a).   +  = 

           = 0

           =  =  = .

          So, the two roots are   =  = 3  and   =  = .



Case b).   +  = 

           = 0

           =  =  = .

          So, the two roots are   =  = 2  and   =  = .


ANSWER.  The four roots are   ,  ,  2  and  3.

Solved.


The lesson to learn

    From this post learn on how to solve palindromic equations.

    Every palindromic equation of the degree 4 can be solved in this way.


The major steps of the solution are :

    a)  Divide both sides by  ;

    b)  Introduce new variable  u = x + ;

    c)  Reduce the equation to a quadratic equation relative new variable u  and solve it getting two roots    and  ;

    d)  Then find  x  by solving two equations   =   and   = .

Again :
    Every palindromic equation of the degree 4 can be solved in this way.


Answer by MathTherapy(10556)   (Show Source): You can put this solution on YOUR website!

Solve 6x⁴ - 35x³ + 62x² - 35x + 6 = 0
RATIONAL ROOT THEOREM produces 2 zeroes: 2 and 3. Therefore, 2 of the expression's factors are: (x - 2) and (x - 3). 
FOILing these 2 factors results in trinomial: x2 - 5x + 6
Now, when 6x4 - 35x3 + 62x2 - 35x + 6 is divided by x2 - 5x + 6, we get: 6x2 - 5x + 1. Factoring 6x2 - 5x + 1 gives us: (3x - 1)(2x - 1).
Therefore, 6x4 - 35x3 + 62x2 - 35x + 6 = 0 becomes: (3x - 1)(2x - 1)(x - 2)(x - 3) = 0 and the solutions are:
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