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5.5. Apply the Remainder and Factor Theorems. What you should learn:. Goal. 1. Divide polynomials and relate the result to the remainder theorem and the factor theorem. using Long Division Synthetic Division. Goal. 2. Factoring using the “Synthetic Method”. Goal. 3.
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5.5 Apply the Remainder and Factor Theorems Whatyou should learn: Goal 1 Divide polynomials and relate the result to the remainder theorem and the factor theorem. • using Long Division • Synthetic Division Goal 2 Factoring using the “Synthetic Method” Goal 3 Finding the other ZERO’s when given one of them. A1.1.5 5.5 The Remainder and Factor Theorem
Divide using the long division ex) x + 7 - ( ) - ( ) 6.5 The Remainder and Factor Theorem
Divide using the long division with Missing Terms ex) - ( ) - ( ) - ( )
Synthetic Division To divide a polynomial by x - c 1. Arrange polynomials in descending powers, with a 0 coefficient for any missing term. 2. Write c for the divisor, x – c. To the right, write the coefficients of the dividend. 3 1 4 -5 5
3 1 4 -5 5 3. Write the leading coefficient of the dividend on the bottom row. 1 4. Multiply c (in this case, 3) times the value just written on the bottom row. Write the product in the next column in the 2nd row. 3 1 4 -5 5 3 1
5. Add the values in the new column, writing the sum in the bottom row. 3 1 4 -5 5 3 add 1 7 6. Repeat this series of multiplications and additions until all columns are filled in. 3 1 4 -5 5 21 3 add 16 7 1
7. Use the numbers in the last row to write the quotient and remainder in fractional form. The degree of the first term of the quotient is one less than the degree of the first term of the dividend. The final value in this row is the remainder. 3 1 4 -5 5 48 3 21 add 1 7 16 53
Synthetic Division To divide a polynomial by x - c Example 1) -1 1 4 -2 -3 -1 1 3 -5
Synthetic Division To divide a polynomial by x - c Example 2) 2 1 0 -5 7 -2 4 2 1 2 5 -1
Factoring a Polynomial (x + 3) Example 1) given that f(-3) = 0. 2 11 18 9 -3 -6 -15 -9 2 5 3 0 multiply Because f(-3) = 0, you know that (x -(-3)) or (x + 3) is a factor of f(x).
Factoring a Polynomial (x - 2) Example 2) given that f(2) = 0. 1 -2 -9 18 2 0 2 -18 1 0 -9 0 multiply Because f(2) = 0, you know that (x -(2)) or (x - 2) is a factor of f(x).
Reflection on the Section If f(x) is a polynomial that has x – a as a factor, what do you know about the value of f(a)? assignment
5.6 Finding Rational Zeros Whatyou should learn: Goal 1 Find the rational zeros of a polynomial. L1.2.1 5.6 Finding Rational Zeros
The Rational Zero Theorem Find the rational zeros of solution List the possible rational zeros. The leading coefficient is 1 and the constant term is -12. So, the possible rational zeros are: 5.6 Finding Rational Zeros
Example 1) Find the Rational Zeros of solution List the possible rational zeros. The leading coefficient is 2 and the constant term is 30. So, the possible rational zeros are: Notice that we don’t write the same numbers twice 5.6 Finding Rational Zeros
Use Synthetic Division to decide which of the following are zeros of the function 1, -1, 2, -2 Example 2) -2 1 7 -4 -28 28 -10 -2 1 5 -14 0 x = -2, 2 5.6 Finding Rational Zeros
Find all the REAL Zeros of the function. Example 3) 1 1 4 1 -6 5 6 1 1 5 6 0 x = -2, -3, 1 5.6 Finding Rational Zeros
Find all the Real Zeros of the function. Example 4) 2 1 1 1 -9 -10 6 14 10 2 1 3 7 5 0 -1 1 3 7 5 -2 -5 -1 1 2 5 0 5.6 Finding Rational Zeros
-1 1 3 7 5 -2 -5 -1 1 2 5 0 x = 2, -1 5.6 Finding Rational Zeros
Reflection on the Section How can you use the graph of a polynomial function to help determine its real roots? assignment 5.6 Finding Rational Zeros
5.7 Apply the Fundamental Theorem of Algebra Whatyou should learn: Goal 1 Use the fundamental theorem of algebra to determine the number of zeros of a polynomial function. THE FUNDEMENTAL THEOREM OF ALGEBRA If f(x) is a polynomial of degree n where n > 0, then the equation f(x) = 0 has at least one root in the set of complex numbers. L2.1.6 5.7 Using the Fundamental Theorem of Algebra
Find all the ZEROs of the polynomial function. Example 1) -5 1 5 -9 -45 45 0 -5 1 0 -9 0 x = -5, -3, 3 5.7 Using the Fundamental Theorem of Algebra
Decide whether the given x-value is a zero of the function. , x = -5 Example 1) -5 1 5 1 5 -5 0 -5 1 0 1 0 So, Yes the given x-value is a zero of the function. 5.7 Using the Fundamental Theorem of Algebra
Write a polynomial function of least degree that has real coefficients, the given zeros, and a leading coefficient of 1. -4, 1, 5 Example 1) 5.7 Using the Fundamental Theorem of Algebra
Find ALL the ZEROs of the polynomial function. Example ) x = 2.732 x = -.732
Find ALL the ZEROs of the polynomial function. Example #24) Doesn’t FCTPOLY…Now what?
Find ALL the ZEROs of the polynomial function. Example ) -1 1 -4 4 10 -13 -14 -1 5 -9 -1 14 1 -5 9 1 -14 0 Graph this one….find one of the zeros..
Reflection on the Section How can you tell from the factored form of a polynomial function whether the function has a repeated zero? At least one of the factors will occur more than once. assignment