计算:
(1) x + 2 2 + x x - 4 ;
(2) a b - 1 ÷ a 2 - b 2 2 b .
计算: (1)---(-1 (2)
计算: (1)(﹣21)+(﹣13)﹣(﹣25)﹣(+28) (2)﹣22﹣6÷(﹣2)× (3) (4)
计算: (1) (2) (3) (4)
计算:2sin60°+cos60°-3tan30°.
先化简,再求值,其中满足.