Answer
false
Work Step by Step
Descartes's Rule of Signs (page 384)
Let $f(x)=a_{n}x^{n}+a_{n-1}x^{n-1}+\cdots+a_{2}x^{2}+a_{1}x+a_{0}$
be a polynomial with real coefficients.
1. The number of positive real zeros of $f$ is either
$\mathrm{a}$. the same as the number of sign changes of $f(x)$
or
$\mathrm{b}$. less than the number of sign changes of $f(x)$ by a positive even integer.
If $f(x)$ has only one variation in sign, then $f$ has exactly one positive real zero.
2. The number of NEGATIVE ...
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With four sign changes the number of positive zeros can be
(a) 4
or
(b) 2, or 0
"must have four" is false, there may be less.
