关于丢番图方程ax2+by2=cz2+dw2的整数解

数论中作为勾股定理的推广曾讨论过方程x2 +y2 =z2 +w2 ( 1 )的整数解 (如文 [1 ]、[2 ]) ,文 [2 ]得到了方程 ( 1 )满足 ( x,y,z,w) =1的全部整数解的一组公式 ,但表达式不够简洁。本文将其推广 ,考虑更一般的这类四元二次丢番都方程ax2 +by2 =cz2 +dw2 ( 2 )其中 a,b,c,d均为正整数 ,( a,b,c,d) =1。当知道它的一组不全为零的整数解时 ,来导出它满足 ( x,y,z,w) =1的全部整数解的公式。按所设 ,显然 z,w不会全为 0 ,不妨设 w≠ 0 ,从而方程 ( 2 )可变为a( xw) 2 +b( yw) 2 -c( zw) 2 =d令 X=x/ w,Y=y/ w,Z=z/ w,得a X2 +b Y2 -c Z2 =d …     

广义Ramanujan-Nagell方程x~2+D~m=p~n的解的注记

设a为偶数,p为素数,D=3a~2+1,p=4a~2+1。本文指出了乐茂华文献中的错误,并利用两个对数的线性型上界估计的P-adic形式以及广义Fermat方程的解的一些新结论,证明了方程x~2+D~m=p~n仅有两组正整数解(x,m,n)=(0,1,1),(8a~3+ 3a,1,3)．     

Diophantine方程(a-1)x~2+f(a)=4a~n的一点注记

设a是大于1的正整数,f(a)是a的非负整系数多项式,f(1)=2rp+4,其中r是大于1的正整数,p=2~l-1是Mersenne素数.本文讨论了方程(a-1)x~2+f(a)=4a~n的正整数解(x,n)的有限性,并且证明了:当f(a)=91a+9时,该方程仅当a=5,7和25时分别有解(x,n)=(3,3),(11,3)和(3,4).     

函数方程f_1~n+af_1~mf_2~m+f_2~n=1的整函数解

对函数方程fn1+af1mf2m+fn2=1,其中a∈C/{0},n,m∈N,给出所有可能的非常数整函数解的形式.     

巧求28a+30b+31c=365的非负整数解

《中学生数学》2011年第2期刊发了刘小杰老师的《28a+30b+31c=365的非负整数解》一文,读后深受启发.下文再给出一种更简便的解法,供读者参阅.解不定方程可变形为     

关于不定方程5x(x+1)(x+2)(x+3)=9y(y+1)(y+2)(y+3)

运用pell方程、递归序列、二次平方剩余的方法,并使用数学软件Mathematica的计算,求出了丢番图方程5x(x+1)(x+2)(x+3)=9y(y+1)(y+2)(y+3)的所有20组整数解,其中只有一组正整数解为(x,y)=(6,5).     

关于Diophantine方程(a~n-1)((a+1)~n-1)=x~2

本文研究了指数Diophantine方程(an-1)((a+1)n-1)=x2的正整数解(n,x),其中a是大于1的正整数.运用初等数论方法证明了:当a≡2或3(mod4)时,该方程无解.     

关于不定方程3x(x+1)(x+2)(x+3)=10y(y+1)(y+2)(y+3)

通过利用pell方程、递归序列、平方剩余、Legendre符号、同余关系等初等证明方法,并利用Mathematica软件对Legendre符号等进行计算,证明了方程3x(x+1)(x+2)(x+3)=10y(y+1)(y+2)(y+3)共有16组整数解,并且无正整数解.     

关于Diophantine方程a~x+b~y=z~2

设a=2~r,b=p~s,其中p是给定的奇素数,r和s是给定的正整数.运用有关三项Diophantine方程和广义Ramanujan-Nagell方程的结果,将方程a~x+~y=z~2的所有正整数解(x,y,z)进行了分类,从而得出了这些解的可有效计算的上界.     

矩阵方程AX=A+X有正定解和幂零解的充要条件

给出了矩阵方程AX=A+X有解、实对称解、正定解和幂零解的充要条件.     

矩阵方程X+A^{*}X^{-q}A=Q(q\geq 1)的Hermitian正定解

本文研究矩阵方程X A~*X~(-q)A=Q(q≥1)的Hermitian正定解,给出了存在正定解的充分条件和必要条件,构造了求解的迭代方法.最后还用数值例子验证了迭代方法的可行性和有效性.     

离散时间代数Riccati方程的解矩阵的下界与上界

本文讨论离散时间代数Ｒｉｃｃａｔｉ方程ＡＴＸＡ－Ｘ－（ＡＴＸＢ＋Ｌ）（Ｒ＋ＢＴＸＢ）＾－１（ＬＴ＋ＢＴＸＡ）＋Ｑ＝０的唯一对称正定解的上界和下界。     

关于矩阵方程X+A*X-1A=P的解及其扰动分析

考虑非线性矩阵方程X＋A^＊（X^-1）A=P其中A是n阶非奇异复矩阵,P是n阶Hermite正定矩阵．本文给出了Hermite正定解和最大解的存在性以及获得最大解的一阶扰动界,改进了文[5,6]中的部分结论．     

ON SOLUTIONS OF MATRIX EQUATION AXAT ＋ BYBT=C

By making use of the quotient singular value decomposition (QSVD) of a matrix pair,this paper establishes the necessary and sufficient conditions for the existence of and the expressions for the general solutions of the linear matrix equation AXA^T BYB^T=C with the unknown X and Y, which may be both symmetric, skew-symmetric, nonnegativede finite, positive definite or some cross combinations respectively. Also, the solutions of some optimal problems are derived.     

关于非线性矩阵方程$X^s-A^*X^{-t}A=Q$的Hermitian正定解及其扰动估计

In this paper, the Hermitian positive definite solutions of the nonlinear matrix equation X^s - A^＊X^-tA = Q are studied, where Q is a Hermitian positive definite matrix, s and t are positive integers. The existence of a Hermitian positive definite solution is proved. A sufficient condition for the equation to have a unique Hermitian positive definite solution is given. Some estimates of the Hermitian positive definite solutions are obtained. Moreover, two perturbation bounds for the Hermitian positive definite solutions are derived and the results are illustrated by some numerical examples.     

On the Hermitian positive defnite solution of the nonlinear matrix equation X + A*X −1 A + B*X −1 B = I

In this paper, we study the matrix equation X + A*X ⁻¹ A + B*X ⁻¹ B = I, where A, B are square matrices, and obtain some conditions for the existence of the positive definite solution of this equation. Two iterative algorithms to find the positive definite solution are given. Some numerical results are reported to illustrate the effectiveness of the algorithms. This research supported by the National Natural Science Foundation of China 10571047 and Doctorate Foundation of the Ministry of Education of China 20060532014.     

二次矩阵方程X~2-bX-C=O的正定解

研究二次矩阵方程X2-bX-C=O(b>0,C为n×n阶正定阵)的正定解,证明了解的存在唯一性并且给出了求解方法.     

Backward Perturbation Analysis for the Matrix Equation A~TXA+B~TYB=D

Consider the linear matrix equation A~TXA + B~TYB = D,where A,B are n X n real matrices and D symmetric positive semi-definite matrix.In this paper,the normwise backward perturbation bounds for the solution of the equation are derived by applying the Brouwer fixed-point theorem and the singular value decomposition as well as the property of Kronecker product.The results are illustrated by two simple numerical examples.     

一个来自振动理论反问题的矩阵方程

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