Precalculus Examples

Find the Maximum Number of Real Roots
To find the possible number of positive roots, look at the signs on the coefficients and count the number of times the signs on the coefficients change from positive to negative or negative to positive.
Since there is sign change from the highest order term to the lowest, there is at most positive root (Descartes' Rule of Signs).
Positive Roots:
To find the possible number of negative roots, replace with and repeat the sign comparison.
Multiply by .
Since there are sign changes from the highest order term to the lowest, there are at most negative roots (Descartes' Rule of Signs).
Negative Roots:
The possible number of positive roots is , and the possible number of negative roots is .
Positive Roots:
Negative Roots:
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