anyone know what are the possible number of positive, negative, and complex zeros of f(x) = 2x3 – 5x2 – 6x + 4 ?

Question

anonymous · Answer

no one?

lalaly · Answer

http://www.wolframalpha.com/input/?i=2x3+%E2%80%93+5x2+%E2%80%93+6x+%2B+4+%3F

amistre64 · Answer

descartes might

amistre64 · Answer

the number of positives is at most the number of sign changes of f(x)

the number of negatives is at most the number of sign changes of f(-x)

amistre64 · Answer

you subtract from the "most" by 2s till you get to zero to find the possible number of zeros in each case

amistre64 · Answer

f(x) = +2x3 – 5x2 – 6x + 4
                   ^              ^     ; at most 2 +

f(-x) = -2x3 – 5x2 + 6x + 4
                              ^          ; at most 1 -

amistre64 · Answer

and id say at most 3 complex ... since it is a degree 3 in question