Please find attached image below thanks in advance?

(a)
(-i)⁴ × 3i³
= (-1)⁴i⁴ × 3i³
= (i²)² × 3i²i
= [(√-1)²]² × 3(√-1)²i
= (-1)² × 3(-1)i
= 1 × (-3i)
= -3i


(b)
(4 + 3i)(7 - 3i)
= 4(7 - 3i) + 3i(7 - 3i)
= 28 - 12i + 21i - 9i²
= 28 + 9i - 9i²
= 28 + 9i - 9(√-1)²
= 28 + 9i - 9(-1)
= 28 + 9i + 9
= 37 + 9i

a) [(-i)^4]3[i]^3 = [(-1)^4][i^4]3[i^3] = 3(-1)i = -3i.
b) (4+3i)(7-3i) = 28-9i^2 + i(3*7 -4*3) = (28+9) + 3(7-4)i = 37 + 9i.