将4个数a,b,c,d排成2行,两边各加一条竖直线记成|a b| |a b| |x+1 x-1||c d|,定义|c d|=ad-bc上述记号叫做2阶行列式,若|x-1 x+1|=18求x的值

将4个数a,b,c,d排成2行,两边各加一条竖直线记成|a b| |a b| |x+1 x-1||c d|,定义|c d|=ad-bc上述记号叫做2阶行列式,若|x-1 x+1|=18求x的值
将4个数a,b,c,d排成2行,两边各加一条竖直线记成
|a b| |a b| |x+1 x-1|
|c d|,定义|c d|=ad-bc上述记号叫做2阶行列式,若|x-1 x+1|=18求x的值

将4个数a,b,c,d排成2行,两边各加一条竖直线记成|a b| |a b| |x+1 x-1||c d|,定义|c d|=ad-bc上述记号叫做2阶行列式,若|x-1 x+1|=18求x的值
| a b |
| c d |= ad - bc
所以,
| x+ 1 x-1 |
| x -1 x+1 | = (x+1)^2 - (x -1)^2 = x^2 + 2x + 1 - (x^2 - 2x + 1) = 4x = 18
即 4x = 18,解得 x = 4.5