Question

二道数学题.已知函数y=x^2+2(a+2)x+a^2 的图像与x轴有两个交点,且都在x轴的负半轴上,则a的取值范围,若

Answer 1

1)Δ=4(a+2)2-4a2>0 => a>-1

对称轴：x=-(a+2) a>-2

y轴截距：a2>=0

所以 a>-1

2)5x + 3y = 2 - 3k

9x - 3y = 3k + 12

x=1

5 + 3y = 2 - 3k => k = -1 - y

3 - y = k + 4 => k = -1 - y

a-b = 1 - y = k+2

-3