Question

prove that if x and y are both odd positive integer then x^2 + y^2 is even but not divisible by 4

Answer 1

Put x =3 and y=3 now
Atq
3^2+3^2
=9+9=18 ..which is an even no. But not divisibl by 4
Similarly u can put 5,7.....
And can simply prove