先化简,再求值: ( a - 1 a ) ÷ a - 1 ( a + 1 ) 2 - 1 ,其中 a 满足 a 2 + 3 a - 1 = 0 .
化简:.
计算:.
计算①–2-5+23-9+7 ② ③ ④
(本题6分)计算:
计算: (1) (2)