Answer:
Step-by-step explanation:
(10-4i) (4-5i) (-15+20i)
(10-4i) (4-5i) = 10*(4-5i) - 4i*(4-5i)
= 10*4 - 10*5i - 4i*4 + 4i*5i
= 40 - 50i - 16i + 20i² =40 - 66i + 20*-1 {i² =-1}
= 40 - 66i -20
= 20 - 66i
(20 - 66i) (-15 + 20i) = 20*(-15 + 20i) - 66i*(-15 + 20i)
= -300 - 400i + 990i - 1320i²
= -300 - 400i + 990i - 1320* (-1)
= -300 - 400i + 990i + 1320
= 1020 + 590i
