The four numbers a, B, C and D are arranged in two rows and two columns, and a vertical line is added on each side to mark them as ABCD. Adcb = ad BC is defined, The four numbers a, B, C and D are arranged in two rows and two columns, and a vertical line is added on each side to mark them as | a B |, which is defined as | a B | = ad BC, The above notation is called a determinant of order 2 |x+1 x-1| |1-x x + 1 | = 6, then x= By the way, how did you get it

The four numbers a, B, C and D are arranged in two rows and two columns, and a vertical line is added on each side to mark them as ABCD. Adcb = ad BC is defined, The four numbers a, B, C and D are arranged in two rows and two columns, and a vertical line is added on each side to mark them as | a B |, which is defined as | a B | = ad BC, The above notation is called a determinant of order 2 |x+1 x-1| |1-x x + 1 | = 6, then x= By the way, how did you get it

It can be expressed by conditions
(x+1)(x+1)-(x-1)(1-x)=6
x^2+2x+1+(x^2-2x+1)=6
2x^2=4
x^2=2
x=±√2

If the numerator is ABCD, the denominator is! ABCD! ("!" means absolute value) the result is equal to 1, what are the ABCD respectively: please advise!

ABCD / | ABCD | = 1, we can get ABCD ＞ 0

Zhang Hao and his parents play on the seesaw. The sum of their weight is 138kg. Zhang Hao, who weighs only half of his mother's, sits on the seesaw with his mother

Zhang Hao and his parents play on the seesaw. The sum of their weight is 138kg. Zhang Hao, who weighs only half of his mother's, sits on one end of the seesaw with his mother, while his father sits on the other end. At this time, his father's end is still on the ground. Can you figure out how much Zhang Hao's weight should be less than? If Zhang Hao's weight is XKG, his mother's weight is 2xkg