Mathematical warfare at its finest! On the left, we have the complex number enthusiasts insisting that x² + 1 = 0 gives us i and -i as solutions. Meanwhile, the modular arithmetic gang on the right is smugly pointing out that in Z₅ (integers modulo 5), the answers are actually 2 and 3.
That's because 2² = 4, plus 1 equals 5, which is 0 in mod 5. Similarly, 3² = 9, which is 4 in mod 5, plus 1 equals 5, which is again 0.
Nothing like watching mathematicians fight over number systems while the rest of us wonder why they weren't invited to more parties in college.