We know, from enunciation, that the integer numbers x, y are positive.
To perform the addition of the fractions from the left side, we'll calculate the least common denominator:
LCD = x^2*y^2
Now, we'll multiply each fraction by the needed value, in order to get x^2*y^2 at denominator.
y^2/x^2*y^2 + x*y/x^2*y^2 + x^2/x^2*y^2 = 1
(y^2 + xy + x^2)/x^2*y^2 = 1
We'll cross multiply and we'll get:
y^2 + xy + x^2 = x^2*y^2
We'll multiply (x-y) both sides:
(x-y)(y^2 + xy + x^2) = (x-y)*x^2*y^2
We'll get to the left a difference of cubes:
x^3 - y^3 = x^3*y^2 - x^2*y^3
Assuming that x=y=1 => 1-1=1-1=0
Assuming that x=y=2 => 8-8 = 8*4 - 4*8 = 0
Assuming that x`!=` y, such as x = 2 and y = 3.
x^3 - y^3 = 8-27 = -19
x^3*y^2 - x^2*y^3 = 8*9 - 4*27 = -36
For any x y>0, x,y Z, the given expression is not an identity, while for integer positive values of x and y, the given expression does represent an identity.