数学
         
语言:中文    Language:English
求逆矩阵:
    输入一个可逆矩阵,每个元用逗号隔开,每行用分号结尾。
    注意,不支持支持数学函数和变量。
    当前位置:线性代数 >求逆矩阵 >逆矩阵计算历史 >答案

$$\begin{aligned}&\\ \color{black}{计算矩阵}& \ \ \begin{pmatrix} &5\ &6\ &8\ &10\ &12\ \\ &6\ &8\ &10\ &12\ &15\ \\ &8\ &12\ &15\ &20\ &24\ \\ &12\ &15\ &20\ &24\ &25\ \\ &15\ &20\ &24\ &25\ &30\ \end{pmatrix}\color{black}{的逆矩阵。}\\ \\解:&\\ &\begin{pmatrix} &5\ &6\ &8\ &10\ &12\ \\ &6\ &8\ &10\ &12\ &15\ \\ &8\ &12\ &15\ &20\ &24\ \\ &12\ &15\ &20\ &24\ &25\ \\ &15\ &20\ &24\ &25\ &30\ \end{pmatrix}\\\\&\color{grey}{用矩阵的初等变换来求逆矩阵:}\\&\left (\begin{array} {cccccc | ccccc} &5\ &6\ &8\ &10\ &12\ &1\ &0\ &0\ &0\ &0\ \\ &6\ &8\ &10\ &12\ &15\ &0\ &1\ &0\ &0\ &0\ \\ &8\ &12\ &15\ &20\ &24\ &0\ &0\ &1\ &0\ &0\ \\ &12\ &15\ &20\ &24\ &25\ &0\ &0\ &0\ &1\ &0\ \\ &15\ &20\ &24\ &25\ &30\ &0\ &0\ &0\ &0\ &1\ \\\end{array} \right )\\\\&\color{grey}{将已知矩阵化为上三角矩阵}\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &5\ &6\ &8\ &10\ &12\ &1\ &0\ &0\ &0\ &0\ \\ &0\ &\frac{4}{5}\ &\frac{2}{5}\ &0\ &\frac{3}{5}\ &-\frac{6}{5}\ &1\ &0\ &0\ &0\ \\ &0\ &\frac{12}{5}\ &\frac{11}{5}\ &4\ &\frac{24}{5}\ &-\frac{8}{5}\ &0\ &1\ &0\ &0\ \\ &0\ &\frac{3}{5}\ &\frac{4}{5}\ &0\ &-\frac{19}{5}\ &-\frac{12}{5}\ &0\ &0\ &1\ &0\ \\ &0\ &2\ &0\ &-5\ &-6\ &-3\ &0\ &0\ &0\ &1\ \\\end{array} \right )\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &5\ &6\ &8\ &10\ &12\ &1\ &0\ &0\ &0\ &0\ \\ &0\ &\frac{4}{5}\ &\frac{2}{5}\ &0\ &\frac{3}{5}\ &-\frac{6}{5}\ &1\ &0\ &0\ &0\ \\ &0\ &0\ &1\ &4\ &3\ &2\ &-3\ &1\ &0\ &0\ \\ &0\ &0\ &\frac{1}{2}\ &0\ &-\frac{17}{4}\ &-\frac{3}{2}\ &-\frac{3}{4}\ &0\ &1\ &0\ \\ &0\ &0\ &-1\ &-5\ &-\frac{15}{2}\ &0\ &-\frac{5}{2}\ &0\ &0\ &1\ \\\end{array} \right )\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &5\ &6\ &8\ &10\ &12\ &1\ &0\ &0\ &0\ &0\ \\ &0\ &\frac{4}{5}\ &\frac{2}{5}\ &0\ &\frac{3}{5}\ &-\frac{6}{5}\ &1\ &0\ &0\ &0\ \\ &0\ &0\ &1\ &4\ &3\ &2\ &-3\ &1\ &0\ &0\ \\ &0\ &0\ &0\ &-2\ &-\frac{23}{4}\ &-\frac{5}{2}\ &\frac{3}{4}\ &-\frac{1}{2}\ &1\ &0\ \\ &0\ &0\ &0\ &-1\ &-\frac{9}{2}\ &2\ &-\frac{11}{2}\ &1\ &0\ &1\ \\\end{array} \right )\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &5\ &6\ &8\ &10\ &12\ &1\ &0\ &0\ &0\ &0\ \\ &0\ &\frac{4}{5}\ &\frac{2}{5}\ &0\ &\frac{3}{5}\ &-\frac{6}{5}\ &1\ &0\ &0\ &0\ \\ &0\ &0\ &1\ &4\ &3\ &2\ &-3\ &1\ &0\ &0\ \\ &0\ &0\ &0\ &-2\ &-\frac{23}{4}\ &-\frac{5}{2}\ &\frac{3}{4}\ &-\frac{1}{2}\ &1\ &0\ \\ &0\ &0\ &0\ &0\ &-\frac{13}{8}\ &\frac{13}{4}\ &-\frac{47}{8}\ &\frac{5}{4}\ &-\frac{1}{2}\ &1\ \\\end{array} \right )\\\\&\color{grey}{将对角线以上的元素化为0}\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &5\ &6\ &8\ &10\ &0\ &25\ &-\frac{564}{13}\ &\frac{120}{13}\ &-\frac{48}{13}\ &\frac{96}{13}\ \\ &0\ &\frac{4}{5}\ &\frac{2}{5}\ &0\ &0\ &0\ &-\frac{76}{65}\ &\frac{6}{13}\ &-\frac{12}{65}\ &\frac{24}{65}\ \\ &0\ &0\ &1\ &4\ &0\ &8\ &-\frac{180}{13}\ &\frac{43}{13}\ &-\frac{12}{13}\ &\frac{24}{13}\ \\ &0\ &0\ &0\ &-2\ &0\ &-14\ &\frac{280}{13}\ &-\frac{64}{13}\ &\frac{36}{13}\ &-\frac{46}{13}\ \\ &0\ &0\ &0\ &0\ &-\frac{13}{8}\ &\frac{13}{4}\ &-\frac{47}{8}\ &\frac{5}{4}\ &-\frac{1}{2}\ &1\ \\\end{array} \right )\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &5\ &6\ &8\ &0\ &0\ &-45\ &\frac{836}{13}\ &-\frac{200}{13}\ &\frac{132}{13}\ &-\frac{134}{13}\ \\ &0\ &\frac{4}{5}\ &\frac{2}{5}\ &0\ &0\ &0\ &-\frac{76}{65}\ &\frac{6}{13}\ &-\frac{12}{65}\ &\frac{24}{65}\ \\ &0\ &0\ &1\ &0\ &0\ &-20\ &\frac{380}{13}\ &-\frac{85}{13}\ &\frac{60}{13}\ &-\frac{68}{13}\ \\ &0\ &0\ &0\ &-2\ &0\ &-14\ &\frac{280}{13}\ &-\frac{64}{13}\ &\frac{36}{13}\ &-\frac{46}{13}\ \\ &0\ &0\ &0\ &0\ &-\frac{13}{8}\ &\frac{13}{4}\ &-\frac{47}{8}\ &\frac{5}{4}\ &-\frac{1}{2}\ &1\ \\\end{array} \right )\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &5\ &6\ &0\ &0\ &0\ &115\ &-\frac{2204}{13}\ &\frac{480}{13}\ &-\frac{348}{13}\ &\frac{410}{13}\ \\ &0\ &\frac{4}{5}\ &0\ &0\ &0\ &8\ &-\frac{836}{65}\ &\frac{40}{13}\ &-\frac{132}{65}\ &\frac{32}{13}\ \\ &0\ &0\ &1\ &0\ &0\ &-20\ &\frac{380}{13}\ &-\frac{85}{13}\ &\frac{60}{13}\ &-\frac{68}{13}\ \\ &0\ &0\ &0\ &-2\ &0\ &-14\ &\frac{280}{13}\ &-\frac{64}{13}\ &\frac{36}{13}\ &-\frac{46}{13}\ \\ &0\ &0\ &0\ &0\ &-\frac{13}{8}\ &\frac{13}{4}\ &-\frac{47}{8}\ &\frac{5}{4}\ &-\frac{1}{2}\ &1\ \\\end{array} \right )\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &5\ &0\ &0\ &0\ &0\ &55\ &-\frac{950}{13}\ &\frac{180}{13}\ &-\frac{150}{13}\ &\frac{170}{13}\ \\ &0\ &\frac{4}{5}\ &0\ &0\ &0\ &8\ &-\frac{836}{65}\ &\frac{40}{13}\ &-\frac{132}{65}\ &\frac{32}{13}\ \\ &0\ &0\ &1\ &0\ &0\ &-20\ &\frac{380}{13}\ &-\frac{85}{13}\ &\frac{60}{13}\ &-\frac{68}{13}\ \\ &0\ &0\ &0\ &-2\ &0\ &-14\ &\frac{280}{13}\ &-\frac{64}{13}\ &\frac{36}{13}\ &-\frac{46}{13}\ \\ &0\ &0\ &0\ &0\ &-\frac{13}{8}\ &\frac{13}{4}\ &-\frac{47}{8}\ &\frac{5}{4}\ &-\frac{1}{2}\ &1\ \\\end{array} \right )\\\\&\color{grey}{将主对角线元素化为1}\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &1\ &0\ &0\ &0\ &0\ &11\ &-\frac{190}{13}\ &\frac{36}{13}\ &-\frac{30}{13}\ &\frac{34}{13}\ \\ &0\ &\frac{4}{5}\ &0\ &0\ &0\ &8\ &-\frac{836}{65}\ &\frac{40}{13}\ &-\frac{132}{65}\ &\frac{32}{13}\ \\ &0\ &0\ &1\ &0\ &0\ &-20\ &\frac{380}{13}\ &-\frac{85}{13}\ &\frac{60}{13}\ &-\frac{68}{13}\ \\ &0\ &0\ &0\ &-2\ &0\ &-14\ &\frac{280}{13}\ &-\frac{64}{13}\ &\frac{36}{13}\ &-\frac{46}{13}\ \\ &0\ &0\ &0\ &0\ &-\frac{13}{8}\ &\frac{13}{4}\ &-\frac{47}{8}\ &\frac{5}{4}\ &-\frac{1}{2}\ &1\ \\\end{array} \right )\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &1\ &0\ &0\ &0\ &0\ &11\ &-\frac{190}{13}\ &\frac{36}{13}\ &-\frac{30}{13}\ &\frac{34}{13}\ \\ &0\ &1\ &0\ &0\ &0\ &10\ &-\frac{209}{13}\ &\frac{50}{13}\ &-\frac{33}{13}\ &\frac{40}{13}\ \\ &0\ &0\ &1\ &0\ &0\ &-20\ &\frac{380}{13}\ &-\frac{85}{13}\ &\frac{60}{13}\ &-\frac{68}{13}\ \\ &0\ &0\ &0\ &-2\ &0\ &-14\ &\frac{280}{13}\ &-\frac{64}{13}\ &\frac{36}{13}\ &-\frac{46}{13}\ \\ &0\ &0\ &0\ &0\ &-\frac{13}{8}\ &\frac{13}{4}\ &-\frac{47}{8}\ &\frac{5}{4}\ &-\frac{1}{2}\ &1\ \\\end{array} \right )\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &1\ &0\ &0\ &0\ &0\ &11\ &-\frac{190}{13}\ &\frac{36}{13}\ &-\frac{30}{13}\ &\frac{34}{13}\ \\ &0\ &1\ &0\ &0\ &0\ &10\ &-\frac{209}{13}\ &\frac{50}{13}\ &-\frac{33}{13}\ &\frac{40}{13}\ \\ &0\ &0\ &1\ &0\ &0\ &-20\ &\frac{380}{13}\ &-\frac{85}{13}\ &\frac{60}{13}\ &-\frac{68}{13}\ \\ &0\ &0\ &0\ &1\ &0\ &7\ &-\frac{140}{13}\ &\frac{32}{13}\ &-\frac{18}{13}\ &\frac{23}{13}\ \\ &0\ &0\ &0\ &0\ &-\frac{13}{8}\ &\frac{13}{4}\ &-\frac{47}{8}\ &\frac{5}{4}\ &-\frac{1}{2}\ &1\ \\\end{array} \right )\\\\->\ \ &\left (\begin{array} {cccccc | ccccc} &1\ &0\ &0\ &0\ &0\ &11\ &-\frac{190}{13}\ &\frac{36}{13}\ &-\frac{30}{13}\ &\frac{34}{13}\ \\ &0\ &1\ &0\ &0\ &0\ &10\ &-\frac{209}{13}\ &\frac{50}{13}\ &-\frac{33}{13}\ &\frac{40}{13}\ \\ &0\ &0\ &1\ &0\ &0\ &-20\ &\frac{380}{13}\ &-\frac{85}{13}\ &\frac{60}{13}\ &-\frac{68}{13}\ \\ &0\ &0\ &0\ &1\ &0\ &7\ &-\frac{140}{13}\ &\frac{32}{13}\ &-\frac{18}{13}\ &\frac{23}{13}\ \\ &0\ &0\ &0\ &0\ &1\ &-2\ &\frac{47}{13}\ &-\frac{10}{13}\ &\frac{4}{13}\ &-\frac{8}{13}\ \\\end{array} \right )\\\\&\color{grey}{所求的逆矩阵为:}\\&\begin{pmatrix} &11\ &-\frac{190}{13}\ &\frac{36}{13}\ &-\frac{30}{13}\ &\frac{34}{13}\ \\ &10\ &-\frac{209}{13}\ &\frac{50}{13}\ &-\frac{33}{13}\ &\frac{40}{13}\ \\ &-20\ &\frac{380}{13}\ &-\frac{85}{13}\ &\frac{60}{13}\ &-\frac{68}{13}\ \\ &7\ &-\frac{140}{13}\ &\frac{32}{13}\ &-\frac{18}{13}\ &\frac{23}{13}\ \\ &-2\ &\frac{47}{13}\ &-\frac{10}{13}\ &\frac{4}{13}\ &-\frac{8}{13}\ \end{pmatrix}\end{aligned}$$

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矩阵的初等变换:


定义:对矩阵的行(列)施行下列三种变换都成为矩阵的初等变换
(1)互换矩阵两行(列)的位置;
(2)用非零常数λ乘矩阵的某行(列);
(3)将矩阵某行(列)的γ倍加到矩阵的另一行(列)上。



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