N Point Set Contruction
吴波.一个有趣的平面N点组的构造[J].中学数学教学,2022(05):78-79.
Abstract:用初等数论的知识证明了:对任意正整数n(n≥3),在平面上存在n个点,其中任两点之间的距离均为有理数,且任三点不共线,而以其中任意三点为顶点的三角形的面积均为无理数.
Φ(x)=2t
对于正整数n,设φ(n)是Euler函数.这是一类基本而又重要的数论函数,它的各种基本性质一直是数论中引人关注的课题[1].1922年,Carmichael[2]曾经猜测:对于给定的偶数2t,如果方程有解x,则它至少有2个解.这是一个迄今远未解决的难题.本文证实了Carmichael猜想在是奇数时是正确的,并且对此情况完整地解决了方程的求解问题,即证明了:
定理 当t是奇数时,如果t=1,则方程有3个解x=3,4,6;如果t>1,则方程有解的充要条件是存在奇素数p和正整数a,可使当此条件成立时,如果2t+1不是素数,则方程有两个解:;如果2t+1是素数,则方程有4个解:.
Quantifier elimination
含量词的公式(∃y)[x2+y2-3=0∧x+y>0]的意思是:存在实数y,使得x2+y2-3=0和x+y>0同时成立。如果将量词从公式中消去,那么可以得到一个等价的无量词公式x2-3≤0∧[x≥0∨2x2-3<0]。这个公式比原来的公式简单而且明确很多。又譬如,哥德巴赫猜想断言:对任意大于2的偶数,存在两个奇素数,其和为给定正偶数。这个断言也可以用含有量词的公式来加以表述。几年前刚刚证明的Fermat大定理指出:对任意大于2的整数n,不存在正整数x,y,z,使得等式xn+yn=zn成立。这个命题同样可以用含量词的公式加以表示。如果能消去上述两个命题中的全称和存在量词,即可得到等价的永真命题,因而也就给出了命题的证明。
Abel's Test
Abel’s Test | Abel’s Test, Uniform Version
This note is an exposition of Abel’s test on convergence of series.
Theorem 1. Suppose converges and that {an} is a monotone bounded sequence. Then converges.
What is a Gröbner basis?
pdf
A Gröbner basis is a set of multivariate polynomials that has desirable algorithmic properties. Every set of polynomials can be transformed into a Gröbner basis. This process generalizes three familiar techniques: Gaussian elimination for solving linear systems of equations, the Euclidean algorithm for computing the greatest common divisor of two univariate polynomials, and the Simplex Algorithm for linear programming; see [3]. For example, the input for Gaussian elimination is a collection of linear forms such as and the algorithm transforms into the Gröbner basis .
A Gröbner basis is a set of multivariate polynomials that has desirable algorithmic properties. Every set of polynomials can be transformed into a Gröbner basis. This process generalizes three familiar techniques: Gaussian elimination for solving linear systems of equations, the Euclidean algorithm for computing the greatest common divisor of two univariate polynomials, and the Simplex Algorithm for linear programming; see [3]. For example, the input for Gaussian elimination is a collection of linear forms such as and the algorithm transforms into the Gröbner basis .
189 post articles, 21 pages.