
Mark M. answered 01/04/15
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For functions in the form f(x) = ax2 + bx + c, the number and nature of roots is given the by determinant of the qualitative formula, b2 - 4ac.
If the determinant > 0, two unequal real roots
If the determinant = 0, two identical real roots
If the determinant < 0, two unequal complex roots
A model so you can go the other two.
f(x) = x2 - 3x + 8, a = 1, b = -3, c = 8
b2 - 4ac
(-3)2 - 4(1)(8)
9 - 32
-32, therefore there are two unequal complex roots.