According to Descartes' rule of signs, how many possible positive real roots could the following polynomial function have?
f(x)=3x^4-5x^3+5x^2+5x-2

A. 3
B. 3 or none
C. 2 or 0
D. 4

Question

According to Descartes' rule of signs, how many possible positive real roots could the following polynomial function have? 
f(x)=3x^4-5x^3+5x^2+5x-2

A. 3
B. 3 or none
C. 2 or 0
D. 4

shamil98 · Answer

$$f(x) = +3x^4-5x^3+5x^2+5x-2$$
there are three cases where the signs change from positive to negative or negative to positive.

anonymous · Answer

so would it be B? because you do that thing where you subtract 2 from the number of sign changes?

shamil98 · Answer

group 1 : +3x^4 - 5x^3
group 2: -5x^3 + 5x^2
group 3 :+5x-2
so 3 signs in the positive case.

shamil98 · Answer

I think A. if you counted by two's it would be 3 and 1 .

anonymous · Answer

it's 3 or 1 :)