Simplify the following expressions showing the steps:
(9+9.4i)+(-8.6-4i)
(9.4i)(-4i)

a) 17.6 + 5.4i

b) 37.6

Step-by-step explanation:

a) (9 + 9.4i) + (8.6 - 4i)

Collect like terms:

9 + 8.6 + 9.4i - 4i

= 17.6 + 5.4i

b) (9.4i)(-4i)

Expand the brackets:

9.4 * -4 * i *  i

Therefore, i * i = -1

=> (9.4i)(-4i) = -37.6 * -1

= 37.6