1、1,3
2、C
3、B
4、
(2)x₁ = 2,x₂ = -2/3;
(3)x₁ = 1,x₂ = -2/3;
(4)x₁ = 4,x₂ = -1/2;
5、(1)x₁ = x₂= 2;
(2)方程无实数根
6、3或-1
7、D
8、(1)x₁ =
+ 1,x₂ = -
+ 1;
(2)x₁ = 2,x₂ = -1/3;
(3)y₁ = 2,y₂ = -2/9;
(4)
9、(1)x₁ = 2,x₂ = -3/2;
10、(1)2x² + 4x + 3 = 2(x + 1)² + 1,
∵ (x + 1)² ≥ 0,
∴ 2(x + 1)² + 1 > 0,
即2x² + 4x + 3 > 0;
(2)3x² - 5x - 1 - (2x² - 4x - 7)=(x - 1/2)² + 24/3 > 0,
∴ 代数式3x² - 5x - 1的值总大于代数式2x² - 4x - 7的值