1、±1,6,-2.
5、< , >.
6、(C). 7、(A).
8、(A). 9、(D).
10、(B).
11、(1) 5; (2) ±0.9;
12、(1) x = ±10;
(2) ± 1.5;
(3) x = -0.8;
(4) x = -1
13、7.85 cm².
所以 = 3.
15、由(a + b + 1) (a + b - 1) = 24,得(a + b)2 -1 = 24,即a + b = ±5.由(a - b + 1)
(a - b - 1) = 0,得(a - b)² - 1 = 0,即a - b = ±1,
16、阴影部分的面积为24,周长约为32.1.