Wednesday, November 16, 2011

Fun with Mathematics

Yet another proof for Fermat's last theorem
Dr.M.Meyyappan,Dean of Science
Sri Raja Raajan College of Engineering and Technology
Amaravathipudur-630301, Tamilnadu,India

The numeral relation in the form a^n +b^n = c^n is found to exist only when a,b,c and n are all whole
integers provided n = 1 or 2.
When n=1; a+b=c ,then a^n+b^n < c^n for n > or = 2
When n =2 ; a^2+b^2 = c^2  then a^n+b^n> c^n for n <2
                                                     a^n+b^n < c^n for n >2
The problem in the conditional relation a^n+b^n=c^n begins from n = 3 and it prevails for all higher
values n >3 .
a^n+b^n =/=c^n when n > or = 3
Let us assume that a^3 +b^3 = c^3 exists with a,band c are all whole numbers. Since sum of two
cubes is equal to a cube, c>a,c>b, but c <a+b .
The cube of a number x can be expressed as x^3 = (x-1)x(x+1) +x
For any product of three successive numbers ,6 will invariably be a factor, and hence,
x^3 = 6n(x) + x
Applying this fact to the cubical relation assume,we have
a+b-c = 6[n(c)-n(a)-n(b)] = 6n
or a+b = c+6n
For a given a and b, that is for given digital endings of a and b, the digital ending of c cannot
have all possible value, but is fixed ,because the digital ending of c^3 must be equal to the
sum of the digital ending of a^3 and b^3.
Table given below shows that digital ending of c for all possible digital endings of a and b
Digital ending of c in a^3 +b^3 = c^3

a       /    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

According to the requirement of digital endings of the equal power relation, one can assume the
following typical relation as an example.
(10x+7)^3 + (10y+4)^3 = (10z+3)^3
Fermat's last theorem demands that x,y,z all cannot be whole numbers simultaneously to satisfy the
relation. Since c>b>a (or c>a>b) ,one can assume that c =b+m, where m = 1,2,3,......
The acceptable and permitted values of m according to digital ending requirement are
9,19,29..... or in general (10k +9) with k =0,1,2,3,.......
It demands that z = y +1
Since a+b = c+6n
 10(x+y)+11 = 10z +3 + 6n
The digital ending requirement allows only certain quantized value n = (3+5m)
where m = 0,1,2,3,......It demands that x+y= z+1 or x = 2
By introducing these derived conditions, we can express the typical cubical relation in terms of one
variable y.
27^3 + (10y+4)^3 = (10y+13)^3
90y^2 + 153y - 585 = 0
Solving this quadratic equation for y,
y = [-153 + (2340090)^1/2]/180
   = 1.8374708.....   or -3.5374708.....
It gives
27^3 + (22.374708...)^3 = (31.374708...)^3
It clearly shows that when a is taken as whole number, then both b and c cannot be whole
integers in the relation a^3+b^3 = c^3. Hence Fermat's last theorem is true for n = 3.

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