3) 3⁴ - 4*3³*4i + 6*3²*4²i² - 4*3*4³i³ + 4⁴i⁴ = 81 - 432i - 864 + 768i + 256 = -527 + 336i
4) ((2 + 5i)²)²(2+5i) = (4 - 25 + 20i)²(2+5i) = (-21 + 20i)²(2+5i) = (441 - 400 - 840i)(2+5i) = (41 - 840i)(2+5i) = 82 - 1680i + 205i + 4200 = 4282 - 1475i
5) (3-i)²(3-i)²(3-i)² = (9-1-6i)(8-6i)(8-6i) = (64 - 36 - 96i)(8-6i) = (28 - 96i)(8-6i) = 224 - 768i - 168i - 576 = -352 - 936i