Question

What are the possible numbers of positive, negative, and complex zeros of f(x) = 2x^3 – 3x^2 + 4x + 5 ?

Answer 1

http://www.purplemath.com/modules/drofsign.htm

Answer 2

two changes in sign, so either 2 or no positive zeros

Answer 3

\[f(-x)=-2x^3 – 3x^2 - 4x + 5 \]one change of sign, so one or no negative zeros. and there are at most 3 zeros. and one has to be real.