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Worksheet Weekly Practice 10

Instructions: You may type up or handwrite your work, but it must be neat, professional, and organized and it must be saved as a PDF file and uploaded to the appropriate Gradescope assignment. Use a scanner or scanning app to convert handwritten work on paper to PDF. I encourage you to type your work using the provided template.
All tasks below must have a complete solution that represents a good-faith attempt at being right to receive engagement credits. If your submission is complete and turned in on time, you will receive full engagement credit for the assignment. All other submissions will receive zero engagement credit. Read the guidelines at Grading Specifications carefully.
To abide by the class academic honesty policy, your work should represent your own understanding in your own words. If you work with other students, you must clearly indicate who you worked with in your submission. The same is true for using tools like generative AI although I strongly discourage you from using such tools since you need to build your own understanding here to do well on exams.

True/False, Multiple Choice, & Fill-In.

For these problems a justification is not required for credit, but it may be useful for your own understanding to include one. True/False problems should be marked True if the statement is always true, and False otherwise. Multiple choice problems may have more than one correct answer if that is indicated in the problem statement; be sure to select all that apply. Fill-in problems require a short answer such as a number, word, or phrase.

Short Response.

Your responses to these questions should be complete solutions with justifications, as per the Grading Specifications.
Problem Specs/Notes: This problem needs a clear application of an irreducibility test or a demonstrated factorization into non-unit factors for each polynomial for a Success.

5.

Let \(p\) be a prime.

(a)

Show that the number of reducible polynomials over \(\Z_p\) of the form \(x^2+ax+b\) is \(p(p+1)/2\text{.}\)

(b)

Determine the number of reducible quadratic polynomials over \(\Z_p\text{.}\)

(c)

Determine the number of irreducible quadratic polynomials over \(\Z_p\) of the form \(x^2+ax+b\text{.}\)

(d)

Determine the number of irreducible quadratic polynomials over \(\Z_p\text{.}\)
Problem Specs/Notes: This problem needs complete and careful counts in each part for a Success. Do use earlier parts to inform your responses to later parts.

6.

In \(\Z[i]\text{,}\) show that \(3\) is irreducible but \(2\) and \(5\) are not.
Problem Specs/Notes: This problem needs a demonstrated factorization into non-unit factors for the non-irreducibles, including justification of why the factors are not units for a Success. It also needs an explanation of why no factorization of \(3\) is possible.

7.

Show that \(3x^2+4x+3\in \Z_5[x]\) factors as \((3x+2)(x+4)\) and as \((4x+1)(2x+3)\text{.}\) Explain why this does not contradict the fact that \(F[x]\) is a unique factorization domain for any field \(F\text{.}\)