先化简,再求值: x x - 3 ⋅ x 2 - 9 - 3 x ,其中x=2.
计算: | - 1 | - 3 tan 45 ∘ + 12 - 3 0 .
解不等式组: 2x - 1 > x + 1 3 ( x - 2 ) - x ≤ 4 .
计算: - ( - 4 ) + | - 5 | + 1 2 - 3 0 - 4 tan 45 ∘ .
计算: 3 25 + ( - 2 ) 3 - ( π - 3 ) 0 .