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Rational Root Theorem. No craziness here! We’re all rational . Skeeter Parker Berrien High School Fall 2013. Rational Root Theorem: The Basics. Start by making certain the equation is in descending order and set = 0.
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Rational Root Theorem No craziness here! We’re all rational. Skeeter Parker Berrien High School Fall 2013
Rational Root Theorem: The Basics • Start by making certain the equation is in descending order and set = 0. • The degree of the equation tells you the MOST number of roots you can have. (e.g.: 4th degree can have no more than 4 roots)
The Basics (continued) • There may be less roots if multiplicity is involved. Multiplicity means an individual root actually works more than once. • Multiplicity occurs with perfect square trinomials (among others).
The List of Possibles • Start by making your list of possible roots. Do this by taking ALL factors (+ and − ) of the last term and placing them over ALL factors of the first coefficient. • Put the positives on one row and the negatives on another. This will make things easier later.
Using the List of Possibles • Use synthetic division to find a root. A number is a root if the remainder is zero. This trial and error may take a while. • Once you find a root, reduce the equation. Revisit your list of possible roots, and mark out those which are no longer possible.
Reducing the Equation • Reduce the equation each time you find another root. The goal is to get to a quadratic equation. • Some websites will tell you to keep using the original equation, but this will not help you when you have to find imaginary or irrational roots.
What are you finding? • Read the instructions! They may ask for: • Rational roots only • Real roots only • All roots
Finding Rational Roots Only • If you are asked only to find the RATIONAL roots, you are finished when you have exhausted the list of possibles. • No radicals or imaginaries!
Finding Real Roots Only • If asked to find the REAL roots, you are finished if the quadratic formula yields a negative number under the radical. • May include radicals! • No imaginaries!
Finding All Roots • Finding ALL roots means you have found root after root, reducing the equation along the way until you get a quadratic equation that either gets factored or completely solved by the use of quadratic formula.
Our Goal • Once you get to a quadratic you can either factor or use quadratic formula to find the remaining two roots. • After you have found all roots, put them all in a solution set.