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a)Which of the residues $0, 1, 2, \ldots, 11$ satisfy the congruence $3x \equiv 0 \pmod{12}?$Give your answer as a list, separated by commas, in order from least to greatest.

 

b)Which of the residues $0, 1, 2, 3, 4$ satisfy the congruence $x^5 \equiv x \pmod{5}?$Give your answer as a list, separated by commas, in order from least to greatest.

 

c)Which of the residues $0, 1, 2, 3, 4, 5$ satisfy the congruence $x^2 + 3x + 2 \equiv 0 \pmod{6}?$Give your answer as a list, separated by commas, in order from least to greatest.

 Apr 23, 2016
 #1
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a)Which of the residues   \( 0, 1, 2, \ldots, 11\)

satisfy the congruence \(3x \equiv 0 \pmod{12}?\)

Give your answer as a list, separated by commas, in order from least to greatest.

 

I am not sure what you mean by reidues??

\(3x \equiv 0 \pmod{12}?\)

Only x=0 and x= multiples of 4 would make this true.  So x=0,4,8

 

 

b)Which of the residues $0, 1, 2, 3, 4$ satisfy the congruence     \(x^5 \equiv x \pmod{5}? \)$Give your answer as a list, separated by commas, in order from least to greatest.

0^0=0  satisfies

1^5=1  satisfies

2^5=32=2 mod5    satisfies

3^5=243= 3mod5    satisfies

4^5=1024=4mod5   satisfies

Nothing bigger will satisfy.

x=0,1,2,3,4   will all satisfy this equation.

 

 

c)Which of the residues $0, 1, 2, 3, 4, 5$ satisfy the congruence

\(x^2 + 3x + 2 \equiv 0 \pmod{6}? \)

Give your answer as a list, separated by commas, in order from least to greatest.

 

\(x^2 + 3x + 2 \equiv 0 \pmod{6}?\\ ​​If \;x=0\\ 0 + 0 + 2 \equiv 2 \pmod{6}?\qquad \mbox{Does not satisfy}\\ ​​If \;x=1\\ 1 + 3+ 2 \equiv 0 \pmod{6}?\qquad \mbox{DOES satisfy}\\ ​​If \;x=2\\ 4 + 6 + 2=12 \equiv 0 \pmod{6}?\qquad \mbox{DOES satisfy}\\ ​​If \;x=3\\ 9 + 9 + 2=20 \equiv 2 \pmod{6}?\qquad \mbox{Does not satisfy}\\ ​​If \;x=4\\ 16 + 12 + 2=30 \equiv 0 \pmod{6}?\qquad \mbox{DOES satisfy}\\ ​​If \;x=5\\ 25 + 15 + 2=42 \equiv 0 \pmod{6}?\qquad \mbox{DOES satisfy}\\\)

 

 

So x=1,2,4,5  satisfy the equality.

 

You should check this.  If you need more explanation then ask for it :)

 Apr 23, 2016

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