Real roots is defined by...

Hey everybody,

I'm new here. I'm working on studying and taking practice tests for the College Algebra CLEP test. Basically what CLEP tests do is, if you pass them, you don't end up having to take that class in college (of course, certain colleges accept certain CLEPs as equivalents for their classes, etc, etc).

Anyway, I'm sort of stumped by these real roots of polynomials and crap. Take a look at this question from the practice test:

Quote:

The set of all values of b for which the equation 4x^2 + bx + 1= 0 has either one real root or two real roots is defined by

(A) b > 4

(B) b < 4

(C) b >= 1 or b <= -1

(D) b > 4 or b < -4

(E) b >= 4 or b <= 4 **<- CORRECT ANSWER**

I'm pretty good with polynomials but I haven't a clue of how they reached this answer. In the shortest of words (if at all possible, lol) how did they reach this answer and conclusion? Could somebody spell it out or direct me to a resource where this concept is demonstrated? Thanks. :)