Question

Multiply and simplify the product.

2i(4 – 5i)
Select the product.

a. –2i

b. 2i

c. –10 + 8i

d. 10 + 8i

Answer 1

2i times 4 equals 8i, i times i equals -1 so 2i times -5i equals 10 since the two negatives cancel out. So your final answer is D 10+8i.

Answer 2

D

Explanation:

This is a complex number simplification

• Also,
  `i=√(-1) \\i^(2)=√(-1) √(-1) \\i^(2)=-1`

We can use the distributive property as the first step. The property is:

`a(b+c)=ab+ac`

So we have:

`2i(4-5i)\\=8i-10i^(2)`

Since
`i^(2)=-1`, we can write:

`8i-10(-1)\\=8i+10`

Option D is correct.