计算: 12 + | 3 - 3 | - ( 1 3 ) - 1 .
( 998 ) 2
a - b 2 - a a - 2 b
( 9 x 4 - 15 x 2 + 6 x ) ÷ 3 x
1 2 x ( 2 x 2 - 4 x + 6 )
2 m + n 2 m - n