中四數學題

The graph of y=ax2-8x-4 lies below the x-axis for all valus of x.Find the range of possible values of a.

lies below the x-axis for all valus of x => no intercept with x - axisthat meansΔ < 0
y=ax2-8x-4
Δ=(-8)2- 4(a)(-4)
=64+16a

64 + 16a < 0
64< -16a
-4 > a

so the range of possible values of a is -4 > a

因你寫得十分復擇,中文來啦.88