If ax2+bx+c,a,b,cϵR, a < 0 has no real zeros and a - b+c<0, then the
value of ac
> 0
< 0
= 0
< -1
f(X) = ax2+bx+c
f(-1) = a - b + c < 0 ⇒ a < 0
f(0) = 0 + 0 + c < 0
ac > 0