# Multiplying complex numbers

• November 28th 2010, 02:55 PM
Rae
Multiplying complex numbers
Write the complex number in the form a + bi.

[1 + sq rt (-2)] * [2 + sq rt (-4)]

The answer I get is:

2 + 2*sq rt(2) + [2 + 2*sq rt(2)]i

The answer in the book is:

[2 - 2*sq rt(2)] + [2 + 2*sq rt(2)]i

I'm sorry if my typing is confusing. I don't know how to type the math symbols.
Thanks for any help.
• November 28th 2010, 03:05 PM
Plato
$(1+\sqrt2i)(2+2i)=2+2\sqrt2i+2i-2\sqrt2=(2-2\sqrt2)+(2\sqrt2+2)i$