complex numbers: (2sqrt[2])/sqrt[18], (-3i)(-4i)

[Guest]

Hi, I have a few questions

Simplify

what did i do wrong?

and

in the back of the book, it sayes the answer is -12, why would this be?

Thanks,
Aka

 

[galactus]

Re: complex numbers

Hi, I have a few questions

Simplify

what did i do wrong?

\(\displaystyle \L\\\frac{2\sqrt{2}}{\sqrt{18}}\)

But, \(\displaystyle \L\\\sqrt{18}=3\sqrt{2}\)

So, you have:

\(\displaystyle \L\\\frac{2\sout{\sqrt{2}}}{3\sout{\sqrt{2}}}=\frac{2}{3}\)



and

in the back of the book, it sayes the answer is -12, why would this be?

Thanks,
Aka

Because i*i=-1 and (-3)(-4)=12, therefore 12*(-1)=-12

 

[Guest]

Because i*i=-1 and (-3)(-4)=12, therefore 12*(-1)=-12

so you always mulitple the i seperatly?

 

[Guest]

why would there be an i in this answer if there was no negative under the root?