Finding x=5: Solving 6x+3=1 in ℤ8 | Homework Help

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Homework Help Overview

The problem involves solving the equation 6x + 3 = 1 in the context of modular arithmetic, specifically within ℤ8. The original poster notes that the textbook provides two solutions: x = 1 and x = 5, and seeks clarification on how to derive x = 5.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the implications of 6 not being a unit in ℤ8, leading to the equation 6(x - 1) = 0. There is a focus on determining which multiples of 6 are divisible by 8. Questions arise about substituting values from the set [0, 1, 2, 3, 4, 5, 6, 7] for x.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem and the implications of the modular arithmetic involved. Some guidance has been provided regarding the relationship between the factors of the equation and the divisibility conditions.

Contextual Notes

There is an emphasis on the constraints of working within ℤ8 and the specific properties of the numbers involved, particularly regarding the lack of a unit for 6 in this modular system.

Math9999

Homework Statement


Solve 6x+3=1 in ℤ8.

Homework Equations


None.

The Attempt at a Solution


6x+3=9
6x=6
x=1
-----------
The answers are x=1, or x=5 in the textbook. But how do I get x=5?
 
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Math9999 said:

Homework Statement


Solve 6x+3=1 in ℤ8.

Homework Equations


None.

The Attempt at a Solution


6x+3=9
6x=6
x=1
-----------
The answers x=1, or x=5 in the textbook. But how do I get x=5?
Since ##6 \in \mathbb{Z}_8## is no unit, we cannot divide by ##6##. Thus from ##6x=6## we get ##6(x-1)=0## and we need to find all numbers, for which ##6y=0## in ##\mathbb{Z}_8##. Now which multiples of ##6## are divisible by eight?
 
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So from the set [0, 1, 2, 3, 4, 5, 6, 7], we have to choose a number to substitute x, right?
 
Yes. And solving ##6y=0## (with ##y=x-1##) does this, because by
$$
6y=0 \quad \Leftrightarrow \quad 8\,\vert \, 6y
$$
you can compare the prime factors: three twos on the left and only one on the right.
 
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Thank you.
 

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