Plowing Through Sec. 2.4b with Two New Topics: Synthetic Division Rational Zeros Theorem.
4.4 Rational Root Theorem. Rational Root Theorem give direction in testing possible zeros. Let a 0 x...
-
Upload
anna-sanchez -
Category
Documents
-
view
212 -
download
0
Transcript of 4.4 Rational Root Theorem. Rational Root Theorem give direction in testing possible zeros. Let a 0 x...
4.4 Rational Root 4.4 Rational Root TheoremTheorem
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..
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
Ex 2Ex 2Find ALL of the roots.Find ALL of the roots.
xx33 + 6x + 6x22 – 13x – 6 = 0 – 13x – 6 = 0
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.)
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