Complex number Problem

Algebra

Complex number Problem

Postby Learningforcomp » Thu Oct 22, 2020 2:20 pm

Greetings , I was solving a list of practice exercises when I got to this question, and I quite can't understand what to do about it. Could you please help me?
this is the question

Being a a real number and the imagnary part of the complex number zero, so a is:

(2+i)/(a+2i)

a)-4
b)-4
c)1
d)2
e)4
I appreciate the time you took.
Thank you.
Learningforcomp
 
Posts: 10
Joined: Fri Sep 11, 2020 2:35 pm
Reputation: 0

Re: Complex number Problem

Postby Baltuilhe » Sat Oct 24, 2020 3:53 pm

Good afternoon!

[tex]\frac{2+i}{a+2i}=\frac{2+i}{a+2i}\cdot\frac{a-2i}{a-2i}\\
=\frac{(2+i)(a-2i)}{a^2+2^2}=\frac{2a-4i+ai+2}{a^2+4}\\
=\frac{2a+2+(a-4)i}{a^2+4}[/tex]

Imaginary part is zero:
a=4

I hope to have helped!

Baltuilhe
 
Posts: 91
Joined: Fri Dec 14, 2018 3:55 pm
Reputation: 56


Return to Algebra



Who is online

Users browsing this forum: No registered users and 2 guests