# mult. imaginary numbers

• Aug 18th 2010, 03:50 PM
allsmiles
mult. imaginary numbers
5 - 2i
3 + 8i

for this problem i would like to know if i should mult. both the tope and the bottom by
3 + 8i.

also i already know that (i) to the second power is equal to -1. but how would you work it out?
• Aug 18th 2010, 04:04 PM
skeeter
Quote:

Originally Posted by allsmiles
5 - 2i
3 + 8i

for this problem i would like to know if i should mult. both the tope and the bottom by
3 + 8i.

also i already know that (i) to the second power is equal to -1. but how would you work it out?

multiply numerator and denominator by the conjugate of the denominator ... (3 - 8i)
• Aug 18th 2010, 05:32 PM
pencil09
Quote:

Originally Posted by allsmiles
5 - 2i
3 + 8i

for this problem i would like to know if i should mult. both the tope and the bottom by
3 + 8i.

also i already know that (i) to the second power is equal to -1. but how would you work it out?

$\frac{5-2i}{3+8i} . \frac{3-8i}{3-8i}$