# logic sets help

Printable View

• Feb 1st 2009, 05:22 AM
srk619
logic sets help
can anyone do this question?
• Feb 1st 2009, 05:32 AM
Rapha
Hey

Do you know what Z6 means? What exactly is your question?

(1*1) mod 6 = 1
(1*2) mod 6 = 2
....
(1*5) mod 6 = 5

(2*1) mod 6 = (1*2) mod 6 = 2
(2*2) mod 6 = 4
(2*3) mod 6 = 6 mod 6 = 0
(2*4) mod 6 = 8 mod 6 = 2
(2*5) mod 6 = 10 mod 6 = 4

....

and so on.
Does it help?

Regards, Rapha
• Feb 1st 2009, 05:54 AM
Soroban
Hello, srk619!

Rapha is right . . .
You're expected to know what $\mathbb{Z}_6$ means.
If you don't, you shouldn't have been assigned this problem.

Quote:

Give the multiplication table for $\mathbb{Z}_6$

and hence find all solutions to: . $x^2 \,=\,3\:\text{ in }\mathbb{Z}_6$ or explain why there are none.

. . $\begin{array}{c||c|c|c|c|c|c|}
\times & 0&1&2&3&4&5 \\ \hline \hline
0 & 0&0&0&0&0&0 \\ \hline
1 & 0&1&2&3&4&5 \\ \hline
2 & 0&2&4&0&2&4 \\ \hline
3 & 0&3&0&3&0&3 \\ \hline
4 & 0&4&2&0&4&2 \\ \hline
5 & 0&5&4&3&2&1 \\ \hline\end{array}$

The values for $x^2$ are on the main diagonal,

. . where we see that: . $3\cdot3 \:=\:3\text{ (mod 6)}$

Therefore: . $x = 3$

• Feb 1st 2009, 06:48 AM
srk619
the question is part of Integers, Congruence arithmetic

its something like what is in the diagram