How do you divide 6i72i?

1 Answer
Apr 8, 2016

4453+553i

Explanation:

To divide this fraction we require to rationalise the denominator.

We do this by multiplying numerator/denominator by the complex conjugate of the denominator

If a ± bi is a complex number then

a ∓ bi is it's conjugate

Note that the 'real part' remains unchanged , while the sign of the 'imaginary part' changes.

Also (a+ bi)(a - bi) = a2b2 a real number

and i2=(1)2=1

Now the conjugate of 7 - 2i is 7 + 2i

multiplying numerator / denominator by (7 + 2i)

(6i)(7+2i)(72i)(7+2i)=42+5i+249+4=4453+553i