# Math-Magic Tree example

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• The Trick of a Mathematical Game. The One’s Digit of the Sum of Two Numbers. Decipher the trick of the following mathematical magic.   The Rule of the Game Here is the game. Pick six natural numbers ($1, 2, 3, \dots$) and place them in the yellow discs of the picture below. For example, let's say I have chosen the numbers $7, 5, 3, 2, […] • Quiz 13 (Part 1) Diagonalize a Matrix Let $A=\begin{bmatrix} 2 & -1 & -1 \\ -1 &2 &-1 \\ -1 & -1 & 2 \end{bmatrix}.$ Determine whether the matrix$A$is diagonalizable. If it is diagonalizable, then diagonalize$A$. That is, find a nonsingular matrix$S$and a diagonal matrix$D$such that […] • The Set of Square Elements in the Multiplicative Group$(\Zmod{p})^*$Suppose that$p$is a prime number greater than$3$. Consider the multiplicative group$G=(\Zmod{p})^*$of order$p-1$. (a) Prove that the set of squares$S=\{x^2\mid x\in G\}$is a subgroup of the multiplicative group$G$. (b) Determine the index$[G : S]$. (c) Assume […] • Is the Derivative Linear Transformation Diagonalizable? Let$\mathrm{P}_2$denote the vector space of polynomials of degree$2$or less, and let$T : \mathrm{P}_2 \rightarrow \mathrm{P}_2$be the derivative linear transformation, defined by $T( ax^2 + bx + c ) = 2ax + b .$ Is$T$diagonalizable? If so, find a diagonal matrix which […] • Degree of an Irreducible Factor of a Composition of Polynomials Let$f(x)$be an irreducible polynomial of degree$n$over a field$F$. Let$g(x)$be any polynomial in$F[x]$. Show that the degree of each irreducible factor of the composite polynomial$f(g(x))$is divisible by$n$. Hint. Use the following fact. Let$h(x)$is an […] • Linear Algebra Midterm 1 at the Ohio State University (1/3) The following problems are Midterm 1 problems of Linear Algebra (Math 2568) at the Ohio State University in Autumn 2017. There were 9 problems that covered Chapter 1 of our textbook (Johnson, Riess, Arnold). The time limit was 55 minutes. This post is Part 1 and contains the […] • Is the Trace of the Transposed Matrix the Same as the Trace of the Matrix? Let$A$be an$n \times n$matrix. Is it true that$\tr ( A^\trans ) = \tr(A)$? If it is true, prove it. If not, give a counterexample. Solution. The answer is true. Recall that the transpose of a matrix is the sum of its diagonal entries. Also, note that the […] • Invertible Matrix Satisfying a Quadratic Polynomial Let$A$be an$n \times n$matrix satisfying $A^2+c_1A+c_0I=O,$ where$c_0, c_1$are scalars,$I$is the$n\times n$identity matrix, and$O$is the$n\times n$zero matrix. Prove that if$c_0\neq 0$, then the matrix$A\$ is invertible (nonsingular). How about the converse? […]