Răspuns :
n=361^2-2*(1+2+3+...+360)=
=361^2-2*360*361/2=
=361^2-360*361=
=361*(361-360)=
=361*1=
=361=
=19²
=361^2-2*360*361/2=
=361^2-360*361=
=361*(361-360)=
=361*1=
=361=
=19²
361^2-2*(1+2+3+...+360) = 361^2 -2* (360*361):2= 361^2 - 360*361= 361( 361-360)= 361*1= 361= 19^2 patrat perfect