Tips For Success

Some problems require you to simplify expressions that contain imaginary numbers.

Tip 1

When multiplying binomials, you should use the Distributive Property.

Tip 2

Recall that i 2 = − 1 . i squared , equals negative 1 .

Which expression is equivalent to ( 3 − 4 i ) ( 2 + i ) ? open 3 minus 4 i close open 2 plus i close question mark

1. 2 − 5 i 2 minus 5 i
2. 2 + 5 i 2 plus 5 i
3. 10 − 5 i 10 minus 5 i
4. 10 + 5 i 10 plus 5 i

Think It Through

( 3 − 4 i ) ( 2 + i ) = 6 + 3 i − 8 i − 4 i 2 = 6 − 5 i − 4 ( − 1 ) = 10 − 5 i table with 4 rows and 1 column , row1 column 1 , open , 3 minus 4 i , close . open , 2 plus i , close , row2 column 1 , equals 6 plus 3 i minus 8 i minus 4 , i squared , row3 column 1 , equals 6 minus 5 i minus 4 . open , negative 1 , close , row4 column 1 , equals 10 minus 5 i , end table

The correct answer is C.