Please help! I have a test in a few hours and I don't feel confident about some of my answers or I don't know how to answer some of the questions!

If the complex number x = 3 + bi and |x|^2 = 13, which is a possible value of b?

Question

Please help! I have a test in a few hours and I don't feel confident about some of my answers or I don't know how to answer some of the questions!

If the complex number x = 3 + bi and |x|^2 = 13, which is a possible value of b?

anonymous · Answer

$$|x|^2=a^2+b^2$$

anonymous · Answer

Are there any options

anonymous · Answer

so $$|3+bi|^2=3^2+b^2=13$$ solve for $b$

anonymous · Answer

yes, the options are 
$$9+b^2=13\
b^2=4\b=\pm2$$

anonymous · Answer

Doesnt (3+bi)^2=9+6bi-b?

anonymous · Answer

Yes these are the options:
2
4
9
10
*FYI, i might cut in and out. My school gives an IPad to each kid; instead of using them for educational purposes, kids use them to play games - taking up the WiFi in the process. So, for people like me that are trying to actually get something done: it's hard. I'll do the best i can to keep up, though.

anonymous · Answer

No, isn't it 9+6bi+bi^2.
(3+bi)(3+bi)
FOIL
9+3bi+3bi+bi^2
9+6bi+bi^2

anonymous · Answer

lmao schools these days .... smh
@satellite73 ohhhhh is the reason why you dont do the regular process of foiling is because you only multiply the real parts with real parts and the complex values with complex values?

anonymous · Answer

no, $$|a+bi|=\sqrt{a^2+b^2}$$ so $$|a+bi|^2=a^2+b^2$$

anonymous · Answer

hmmmmm confused as hell -.-
Lemme google this stuff

anonymous · Answer

i though |a+bi| is the absolute value of a+bi

anonymous · Answer

Yes, I'm pretty sure that's right @Heart_Broken_Kid, unless i got something mixed up.

anonymous · Answer

hahaha sattelite is correct ... I just need to see where i went wrong