• April 19th 2010, 02:02 PM
alireza6485
Hello,
I would really appreciate it if someone could please show me how to solve :

Find x when 3(x^2) + 1 ≡ 0 (mod 7).
step by step.
It's from a sample exam I am trying to study..
• April 19th 2010, 02:37 PM
tonio
Quote:

Originally Posted by alireza6485
Hello,
I would really appreciate it if someone could please show me how to solve :

Find x when 3(x^2) + 1 ≡ 0 (mod 7).
step by step.
It's from a sample exam I am trying to study..

The following is done via arithmetic modulo 7:

$3x^2+1=0\Longrightarrow 3x^2=-1=6\Longrightarrow x^2=2\Longrightarrow x=\pm 3\Longrightarrow x_1=3\,,\,x_2=-3=4$

Tonio
• April 19th 2010, 03:32 PM
alireza6485