Math Problem Statement

Use synthetic division and the Remainder Theorem to find the indicated function value. f(x) = 2x^4 - 9x^3 - 3x^2 + 3x + 8, f(-1/2) = ?

Solution

The problem requires finding the value of f(12)f\left(-\frac{1}{2}\right) for the function

f(x)=2x49x33x2+3x+8f(x) = 2x^4 - 9x^3 - 3x^2 + 3x + 8

using synthetic division and the Remainder Theorem.

Steps using Synthetic Division:

  1. Set up for synthetic division: We divide the polynomial by x(12)x - \left(-\frac{1}{2}\right), so we use 12-\frac{1}{2} as the divisor in synthetic division.

  2. Coefficients of the polynomial: Extract the coefficients of f(x)f(x), which are: [2,9,3,3,8][2, -9, -3, 3, 8]

  3. Perform synthetic division:

    • Write down 12-\frac{1}{2} on the left.
    • Set up the row with the coefficients 2,9,3,3,82, -9, -3, 3, 8.
    • Bring down the first coefficient 22.
    • Multiply by 12-\frac{1}{2}, and then add to the next coefficient:
      • 2×(12)=12 \times \left(-\frac{1}{2}\right) = -1; add to 9-9 to get 10-10.
      • 10×(12)=5-10 \times \left(-\frac{1}{2}\right) = 5; add to 3-3 to get 22.
      • 2×(12)=12 \times \left(-\frac{1}{2}\right) = -1; add to 33 to get 22.
      • 2×(12)=12 \times \left(-\frac{1}{2}\right) = -1; add to 88 to get 77.
  4. Interpret the result: The remainder is 77, which is the value of f(12)f\left(-\frac{1}{2}\right) by the Remainder Theorem.

Final Answer:

f(12)=7f\left(-\frac{1}{2}\right) = 7

Let me know if you need further details or explanations! Here are some follow-up questions for practice:

  1. What is the Remainder Theorem, and how is it used in synthetic division?
  2. How can synthetic division be applied to a divisor of the form xcx - c?
  3. Can synthetic division be used for divisors of higher degree, like x22x+1x^2 - 2x + 1?
  4. What happens if the remainder in synthetic division is zero?
  5. How would the process change if you had to find f(12)f\left(\frac{1}{2}\right)?

Tip:

The Remainder Theorem is useful because it allows you to quickly evaluate polynomials at specific values without directly plugging in the numbers!