Please help! Thank you! I will mark brainliest!

1. (x+3i)(x-3i)
x^2 -3xi + 3xi + 9i^2
1 equals 9i^2 + x^2
2. (x-4i)(x+4i)
x^2 + 4xi -4xi -16i^2
2 equals -16i^2 + x^2
3. (x+8i)(x-8i)
x^2 -8ix + 8ix -64i^2
3. equals -64i^2 + x^2
Answers:
1. 9i^2 + x^2
2. -16i^2 + x^2
3. -64i^2 + x^2