Fermat's Last Theorem: A Proof by Contradiction

In this paper I offer an algebraic proof by contradiction of Fermat’s Last Theorem. Using an alternative to the standard binomial expansion, (a+b) n = a n + b Pn i=1 a n−i (a + b) i−1 , a and b nonzero integers, n a positive integer, I show that a simple rewrite of the Fermat’s equation stating the theorem, A p + B p = (A + B − D) p , A, B, D and p positive integers, D < A < B, p ≥ 3 and prime, entails the contradiction, A(B − D) X p−1 i=2 (−D) p−1−i "X i−1 j=1 A i−1−j (A + B − D) j−1 # + B(A − D) X p−1 i=2 (−D) p−1−i "X i−1 j=1 B i−1−j (A + B − D) j−1 # = 0, the sum of two positive integers equal to zero. This contradiction shows that the rewrite has no non-trivial positive integer solutions and proves Fermat’s Last Theorem. AMS 2020 subject classification: 11A99, 11D41 Diophantine equations, Fermat’s equation ∗The corresponding author. E-mail: [email protected] 1 1 Introduction To prove Fermat’s Last Theorem, it suffices to show that the equation A p + B p = C p (1In this paper I offer an algebraic proof by contradiction of Fermat’s Last Theorem. Using an alternative to the standard binomial expansion, (a+b) n = a n + b Pn i=1 a n−i (a + b) i−1 , a and b nonzero integers, n a positive integer, I show that a simple rewrite of the Fermat’s equation stating the theorem, A p + B p = (A + B − D) p , A, B, D and p positive integers, D < A < B, p ≥ 3 and prime, entails the contradiction, A(B − D) X p−1 i=2 (−D) p−1−i "X i−1 j=1 A i−1−j (A + B − D) j−1 # + B(A − D) X p−1 i=2 (−D) p−1−i "X i−1 j=1 B i−1−j (A + B − D) j−1 # = 0, the sum of two positive integers equal to zero. This contradiction shows that the rewrite has no non-trivial positive integer solutions and proves Fermat’s Last Theorem.

Sources of Students’ Difficulties with Proof By Contradiction

The literature on proof by contradiction (PBC) is nearly unanimous in claiming that this proof technique is “more difficult” for students than direct proof, and offers multiple hypotheses as to why this might be the case. To examine this claim and to evaluate some of the hypotheses, we analyzed student work on proof construction problems from homework and examinations in a university “Introduction to Proof” course taught by one of the authors. We also conducted stimulated-recall interviews with student volunteers probing their thought processes while solving these problems, and their views about PBC in general. Our results suggest that the knowledge resources students bring to bear on proof problems, and how these resources are activated, explain more of their “difficulties” than does the logical structure of the proof technique, at least for this population of students.

A Hypothesis Framework for Students’ Difficulties with Proof By Contradiction

In mathematics education, the research on proof by contradiction (PBC) often claims that this activity is more difficult for students than direct proof, or simply difficult in general. Many hypotheses have been offered to support or explain this belief, yet they span a disorientingly wide swath of journal articles, conference papers, dissertations, book chapters, etc. In addition, few attempts have been made to organize these hypotheses or carefully test them. In this paper, we conduct a thorough literature review on PBC, organize existing hypotheses about challenges with PBC into a Hypothesis Framework for (Students’ Difficulty with) Proof By Contradiction (HFPBC), discuss the state of research related to each hypothesis, and offer thoughts on the future study of these hypotheses.

Methods of Mathematical Proof and Logic in Mathematics Courses at the Faculty of Education – Sana'a University

This study aimed to identify the extent to which mathematical proof and logic methods are achieved in mathematics courses for student-teachers at the University of Sana'a. To achieve this objective, the descriptive and analytical method was used. Checklists for analyzing mathematical content according to methods of mathematical proof and logic were developed, and a questionnaire was used to verify the validity of the checklists. The tools were validated by a jury of experts, and the degree of agreement was (98.1%) (85.82%). The tools were applied to a sample of mathematics courses, including mathematical analysis, real analysis and abstract algebra (1), (2). The findings revealed that the most frequent proof methods found in mathematical courses were proof by deduction and transgression (65.86%) of the total methods, followed by proof by mathematical induction (11.75%), and the least frequent was proof by contradiction (9.61%). The courses did not include method of evaluative, critical and reversed proof. The direct method of proof was (82.93%), whereas the occurrence of the indirect proof method was (17.07%). The course content also did not include method of evaluative, critical and reversed proof, and there were statistically significant differences at (0.01), between the weights of the methods of mathematical proof and logic, which were included in the current courses, and the weights that should be included.

Fault Compensation Control of MIMO Nonlinear Systems Subject to Unknown Control Directions

This study is primarily focused on the issue of low-complexity prescribed performance fault compensation for multi-input and multi-output (MIMO) uncertain nonlinear systems with actuator failures, coupling states, and unknown control directions. First of all, proper logarithm-type error conversion functions and smooth orientation functions are linked to design the continuous control signals in the state feedback controller. Then, based on the idea of proof by contradiction, it is shown that the state errors converge to a predictable compact aggregate at the definite rate. Meanwhile, the boundedness of any closed-loop signals might be guaranteed. The simulation example results are delivered to demonstrate the effectiveness of the developed control strategy at last.

Three Proofs that the Square Root of 2 Is Irrational

This short article gives three proofs that the square root of 2 is irrational. The article is written in an expository tutorial format and the background information is provided in brief. The first proof is a simple proof by contradiction and the second and third proofs use field theory from abstract algebra. All three topics are developed and explained. For more details, please see this excellent course at Clemson University.

Teaching and Learning Mathematical Philosophy Through Infinity

Lam [1], explained how mathematics is not only a technical subject but also a cultural one. As such, mathematical proofs and definitions, instead of simply numerical calculations, are essential for students when learning the subject. Hence, there must be a change in Hong Kong’s local teachers’ pedagogies. This author suggests three alternative way to teach mathematical philosophy through infinity. These alternatives are as follows: 1. Teach the concept of a limit in formalism through story telling, 2. Use geometry to intuitively learn infinity through constructivism, and 3. Implement schematic stages for proof by contradiction. Simultaneously, teachers should also be aware of the difficulties among students in understanding different abstract concepts. These challenges include the following: 1. Struggles with the concept of a limit, 2.Mistakes in intuitively computing infinity, and 3. Challenges in handling the method of proof by contradiction. Adopting these alternative approaches, can provide the necessary support to pupils trying to comprehend the above mentioned difficult mathematical ideas and ultimately transform students’ beliefs [2]. One can analyze these changed beliefs against the background of con-ceptual change. According to Davis [3], “this change implies conceiving of teaching as facili-tating, rather than managing learning and changing roles from the sage on the stage to a guide on the side”. As a result, Hong Kong’s academic results in mathematics should hopefully improve.