The four numbers a, B, C and D are arranged in two rows and two columns, and a vertical line is added on both sides to mark them as | a B |, which defines | a B | = ad BC, | C D | C D| 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, |c d| | c d| The above notation is called a determinant of order 2 |x+1 1-x| |1-x x + 1 | = 6, then x= . |A B, definition a B|= |c d| |c d|

The four numbers a, B, C and D are arranged in two rows and two columns, and a vertical line is added on both sides to mark them as | a B |, which defines | a B | = ad BC, | C D | C D| 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, |c d| | c d| The above notation is called a determinant of order 2 |x+1 1-x| |1-x x + 1 | = 6, then x= . |A B, definition a B|= |c d| |c d|

(x+1)^2-(1-x)^2=4x=6 x=1.5