高二数学上册 9.3(二阶行列式)课件 沪教版 课件VIP免费

二阶行列式用消元法解二元线性方程组.,22221211212111bxaxabxaxa12:122a,2212221212211abxaaxaa:212a,1222221212112abxaaxaa，得两式相减消去2x一、二阶行列式的引入;212221121122211baabxaaaa）（，得类似地，消去1x,211211221122211abbaxaaaa）（时，当021122211aaaa方程组的解为，211222112122211aaaabaabx）（3.211222112112112aaaaabbax由方程组的四个系数确定.由四个数排成二行二列（横排称行、竖排称列）的数表)4(22211211aaaa定义定义)5(42221121121122211aaaaaaaa行列式，并记作）所确定的二阶称为数表（表达式即.2112221122211211aaaaaaaaD11a12a22a12a主对角线副对角线对角线法则对角线法则2211aa.2112aa二阶行列式的计算若记,22211211aaaaD.,22221211212111bxaxabxaxa对于二元线性方程组系数行列式.,22221211212111bxaxabxaxa,22211211aaaaD.,22221211212111bxaxabxaxa,2221211ababD.,22221211212111bxaxabxaxa,22211211aaaaD.,22221211212111bxaxabxaxa,2221211ababD.,22221211212111bxaxabxaxa.2211112babaD则二元线性方程组的解为,2221121122212111aaaaababDDx注意分母都为原方程组的系数行列式..2221121122111122aaaababaDDx例例11.12,12232121xxxx求解二元线性方程组解1223D)4(3,07112121D,14121232D,21DDx11,2714DDx22.3721