Dividing Complex Numbers

The conjugate of 9 + 10i is...

• -9 + 10i

• -9 -10i

• 9 - 10i

• -19i

To divide

 $\frac{7+8i}{-1\ +\ i}$  you need to multiply this fraction by...

•  $\frac{-1-i}{-1-i}$  

•  $\frac{-1+i}{-1+i}$  

•  $\frac{1-i}{1-i}$  

•  $\frac{7-8i}{-1-i}$  

This one's tricky... what's the conjugate of -9i? Think of it as 0-9i if it helps.

• 9i

• +0 - 9i

• 81i²

• -81

Now divide... using the conjugate :)

What's the conjugate multiplier of

 $\frac{10\ +2i}{6\ +8i}$  ?

•  $\frac{2i\ -10}{2i\ -10}$  

•  $\frac{6+8i}{-10+2i}$  

•  $\frac{6-8i}{6+8i}$  

•  $\frac{6-8i}{6-8i}$  

Reorder the steps in dividing the complex number

• = 8i

Divide the complexes

What conjugate multiplier should we use?

Kevin says that to divide this complex number you need to multiply the numerator by 7i. John says you have to multiply the numerator and denominator by 7i. Who is correct?

• Kevin

• John

• Fred