Question

Multiply (5 + 3i)(5 − 3i)

16 + 15i

16 − 15i

16

34

Answer 1

D. 34

Explanation:

Answer 2

(5 + 3i)(5 − 3i) = 34

Explanation:

The multiplication of two identical binomials who have different symbol, can be solved using the factoring case of a difference of squares:

`(a-b).(a+b)=a^(2)-b^(2)`

So, in this case:

`(5+3i).(5-3i) = 5^(2)-(3i)^(2)`

`=25-9i^(2)`

Remember that
`i=√(-1)`

So:
`i^(2)=-1`

We replace on the polynomial:

`=25-9.(-1) = 25+9=34`