4.4 Rational Root Theorem. Rational Root Theorem give direction in testing possible zeros. Let a 0 x...

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4.4 Rational Root 4.4 Rational Root Theorem Theorem

Transcript of 4.4 Rational Root Theorem. Rational Root Theorem give direction in testing possible zeros. Let a 0 x...

Page 1: 4.4 Rational Root Theorem. Rational Root Theorem give direction in testing possible zeros. Let a 0 x n + a 1 x n-1 + …a n-1 x + a n = 0 represent a polynomial.

4.4 Rational Root 4.4 Rational Root TheoremTheorem

Page 2: 4.4 Rational Root Theorem. Rational Root Theorem give direction in testing possible zeros. Let a 0 x n + a 1 x n-1 + …a n-1 x + a n = 0 represent a polynomial.

Rational Root Theorem give direction in Rational Root Theorem give direction in testing possible zeros.testing possible zeros.

Let aLet a00xxnn + a + a11xxn-1n-1 + …a + …an-1n-1x + ax + ann = 0 represent a = 0 represent a

polynomial equation of degree n with polynomial equation of degree n with integral coefficients. If a rational number integral coefficients. If a rational number p/q, where p and q have no common p/q, where p and q have no common factors, is a root of the equation, then p is factors, is a root of the equation, then p is a factor of aa factor of ann and q is a factor of a and q is a factor of a00..

Page 3: 4.4 Rational Root Theorem. Rational Root Theorem give direction in testing possible zeros. Let a 0 x n + a 1 x n-1 + …a n-1 x + a n = 0 represent a polynomial.

Ex 1Ex 1List all the possible rational roots List all the possible rational roots then determine the rational roots.then determine the rational roots.

3x3x33 – 13x – 13x22 + 2x + 8 = 0 + 2x + 8 = 0

Page 4: 4.4 Rational Root Theorem. Rational Root Theorem give direction in testing possible zeros. Let a 0 x n + a 1 x n-1 + …a n-1 x + a n = 0 represent a polynomial.

Ex 2Ex 2Find ALL of the roots.Find ALL of the roots.

xx33 + 6x + 6x22 – 13x – 6 = 0 – 13x – 6 = 0

Page 5: 4.4 Rational Root Theorem. Rational Root Theorem give direction in testing possible zeros. Let a 0 x n + a 1 x n-1 + …a n-1 x + a n = 0 represent a polynomial.

Descartes’ Rule of SignsDescartes’ Rule of Signs

Used to determine the possible number of Used to determine the possible number of positive real zeros a polynomial has. positive real zeros a polynomial has. P(x) is a polynomial in descending order. The # P(x) is a polynomial in descending order. The # of positive real zeros is the same as the number of positive real zeros is the same as the number of sign changes of the coefficients or is less than of sign changes of the coefficients or is less than this by an even number.this by an even number.The # of negative real zeros is the same as the The # of negative real zeros is the same as the number of sign changes of the coefficients of P(-number of sign changes of the coefficients of P(-x), or less than by an even number.x), or less than by an even number.(Ignore zero coefficients.)(Ignore zero coefficients.)

Page 6: 4.4 Rational Root Theorem. Rational Root Theorem give direction in testing possible zeros. Let a 0 x n + a 1 x n-1 + …a n-1 x + a n = 0 represent a polynomial.

Ex 3Ex 3find the number of possible positive find the number of possible positive

and negative real zeros for then and negative real zeros for then determine the rational zeros:determine the rational zeros:

P(x) = 2xP(x) = 2x44 – x – x33 – 2x – 2x22 + 5x + 1 + 5x + 1