Linear Diophantine Equation
from the name it's clear that it's an equation of degree 1.
is also an linear Diophantine equation.According to Bézout's identity if equation number (I) holds true.i.e. gcd(a,b)=d satisfies then, there should be an integer solution of this equation.It's true for more than two variables as well.
Lets take an example
As, gcd(14,35)=7 hence Bézout's identity holds true.
Now we can verify it.(x,y)::(-2,1) is an integer solution set of this equation.
Fermat's Last Theorem
If n=2 this equation becomes x^2+y^2=z^2 nothing but Pythagorian triplets of (x,y,z). Infinite numbers of solution exist.
But if n>=3 no solution exists. This is known as Fermat's Last Theorem
this equation is known as Pell's equation, Where n is a non square integer.Trivially x=1, y=0 is one of the solutions of this equation.But there could be other values ,till infinity, as well.
Now by squaring we can write
=>(2x^2+1)^2-n(2xy)^2=1 [If x^2-ny^2=-1]...(I)
or, (2x^2-1)^2-n(2xy)^2=1[If x^2-ny^2=1]....(II)
(I) and (II) are also another form of Pell's equation.
For n>=2, 4/n can be expressed as the summation of three fractional numbers.
Wacław Franciszek Sierpiński generalized this equation and stated that,
for any positive k there exists a number N such that, for all n ≥ N, there exists a solution in positive integers to k/n =1/x+1/y+1/z