Wednesday, January 5, 2011

Fun with mathematics

A simple proof for Fermat’s last theorem
Proof.1
The relation a^n + b^n = c^n where a,b,c and n are all integral
values is true when n takes value either 1 or 2 ,but not existing
for all values n ≥ 3.

Let us suppose that a^3 + b^3 = c^3 is existing. Since cube of
a number x can be expressed as
x^3 = 6k + x
where k is a number ,all cubical relations irrespective of their
reality  must satisfy a condition, the sum of the cube roots in
one side must be greater than by 6 or multiple of 6 with the
sum of the cube roots in the other side of the  numeral relation.
Applying this unique condition to our cubical relation we have,
                                a+b = c +6m    
Rearranging the terms after squaring both sides,

                 a^2+b^2 –c^2-36m^2= 2 [6cm-ab]

(a+c)(a-c) +(b-6m)(b+6m)= (a+c)[-(b-6m)]+(b-6m)(b+6m)
                                           = (b-6m)[b+6m-a-c]
                  (a-6m)(b-6m)=  (ab-6cm)
cubing both sides of  the unique conditional relation,

a^3+b^3+3ab(a+b)= c^3 +216m^3 + 18cn(c+6m)

If a^3+b^3 = c^3 is true, then
72m^3 – (a+b)[ab-6cm]=0
72m^3 = (a+b)(b-6m)(a-6m) must also be true.
When m = 1
72 = (a+b) (a-6)(b-6)
If a and b are odd then c must be even.If a is odd and b is even,
then c must be odd.If the ending digit of a and b is fixed, then c
cannot have all possible ending digit.a^3+b^3=c^3 demands
that the ending digit of the sum of the cubes of a and b must
be equal to the ending digit of the cube of c. 
The following table shows the ending digit of c for the given
ending digit of a and b                                                                                                                    
  ending                       ending digit of a
  digit of_______________________________________________
      b           0     1      2      3       4       5        6        7         8         9  
______________________________________________________

     0           0      1      2      3       4      5        6        7        8          9
     1           1      8      9     2       5       6        3        4        7          0
     2           2      9      6     5       8       7        4        1        0          3
     3           3      2      5     4       1       8        7        0        9          6
     4           4      5      8     1       2       9        0        3        6          7
     5           5      6      7     8       9       0        1        2        3          4
     6           6      3      4     7       0       1        8        9        2          5
     7           7      4      1     0       3       2        9        6        5          8
     8           8      7      0     9       6       3        2        5        4          1
     9           9      0      3     6       7       4        5        8        1          2

For example, if a = 10x+3,b= 10y +5, then c= 10z+8
Substituting this conditional values,we have,
72 = [10(x+y)+8][(10x-3)(10y-1)]
    = [10(x+y)+8][10(x-1)+7][10(y-1)+9]
Since the product of 3 numbers ending with 8,7 and 9 does not
end with 2 ,this auxiliary condition stands as a proof for the
non-existence of the initially assumed cubical relation.
This is true for all values of m. For example when m = 2

576 = [10(x+y)+8][10(x-1)+1][10(y-1)+3]

where LHS ends with 6 while RHS ends with 4,which is
quite absurd for numeral equations.

Proof.2
If a ends with 3 and b ends with 5, then c ends with 8.
Let a = 10x+3, b= 10y+5 and c = 10z +8
Substituting these values in the unique condition of the
cubical relation a+b= c+6m we have,
10(x+y)+8 = 10z + 8 + 6m
10(x+y) = 10z + 6m
m cannot take all possible values. The acceptable values
of m are
m = 5p where p = 1,2,3,4,……
  or x+y = z +3p
when p = 1 x+y = z +3
Since a<c and b<c and a+b>c
X= z then y =3 or in general x = z-q then y = q+3
[10(z-q)+3]^3 +[10(q+3)+5]^3 = (10z+8)^3
When q=0
(10z+3)^3 +35^3 = (10z+8)^3
1000z^3 +900z^2 +270z +27 + 42875
              = 1000z^3 + 2400z^2 +1920z +512
or 1500z^2+1650z – 42390 = 0
         50z^2 +55z – 1413 = 0
The quadratic equation in z does not have any integral solutions .
The possible solution is
    Z =    [-55 ±√ 3025 +282600]/100 = 4.7943895
        = [-11+ 5√457]/20
This is true for all values of p and  q, which concludes that
a^3 + b^3 = c^3 is not true.
There two more proofs,which we will see in the next issue.
I hope my argument is sensible. (meydhanam@gmail.com

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