计算:.
化简: ( a + 1 a - 1 - a a + 1 ) ÷ 3 a + 1 a 2 + a .
计算: ( - 3 ) × ( - 6 ) + | 2 - 1 | + ( 5 - 2 π ) 0
解方程: x + 3 x - 3 - 2 x + 3 = 1 .
计算: ( - 2 ) × 6 + | 3 - 2 | - ( 1 2 ) - 1 .
解分式方程: 2 x - 1 x + 2 = 2 - 3 x - 2 .