# Math Help - Descartes Rule of Signs

1. ## Descartes Rule of Signs

Use Descartes's Rule of Signs to determine the possible number of negative real zeros for the given function.

$g(x)=-3x^7+x^5-x^2+4$

So far I have this:

$g(-x)=-3(-x)^7+1(-x)^5-1(x)^2+4$
$g(-x)=-3x^7-x^5-x^2+4$

1 negative real root.

2. g(x) has -+-+ That's 3, so 3 or 1 positive.

g(-x) has +--+ That's 2, so 2 or 0 negative.

ALL the negative powers change sign for g(-x). You missed the $x^{7}$ term.