Math Problem Statement

If f(x) = 6x^3 - 53x^2 - 14x + 45 and f(9) = 0, then find all of the zeros of f(x) algebraically.

Solution

The problem presented is to find all the zeros of the function f(x)=6x353x214x+45f(x) = 6x^3 - 53x^2 - 14x + 45 given that f(9)=0f(9) = 0, indicating that x=9x = 9 is one of the zeros of the polynomial.

To solve this algebraically using synthetic division:

  1. Set up synthetic division with x=9x = 9 as the divisor.
  2. Write the coefficients of the polynomial: 6,53,14,456, -53, -14, 45.
  3. Perform synthetic division to factor the polynomial into a quotient (a quadratic) and a remainder of 0.
  4. Solve the resulting quadratic equation either by factoring, completing the square, or using the quadratic formula to find the other zeros.

Let's go step by step:

Step 1: Synthetic Division

We set up the synthetic division with x=9x = 9 as the divisor. The coefficients of the polynomial are 6,53,14,456, -53, -14, 45.

9 |  6   -53   -14   45

Perform the division:

  1. Bring down the 6.
  2. Multiply 6×9=546 \times 9 = 54 and add to -53: 53+54=1-53 + 54 = 1.
  3. Multiply 1×9=91 \times 9 = 9 and add to -14: 14+9=5-14 + 9 = -5.
  4. Multiply 5×9=45-5 \times 9 = -45 and add to 45: 45+(45)=045 + (-45) = 0.

So, the result is:

  6   1   -5   0

This gives us a quotient of 6x2+x56x^2 + x - 5 and a remainder of 0, confirming that x=9x = 9 is indeed a root.

Step 2: Solve the Quadratic

Now, we solve 6x2+x5=06x^2 + x - 5 = 0. Using the quadratic formula:

x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

where a=6a = 6, b=1b = 1, and c=5c = -5.

x=1±124(6)(5)2(6)x = \frac{-1 \pm \sqrt{1^2 - 4(6)(-5)}}{2(6)} x=1±1+12012x = \frac{-1 \pm \sqrt{1 + 120}}{12} x=1±12112x = \frac{-1 \pm \sqrt{121}}{12} x=1±1112x = \frac{-1 \pm 11}{12}

Thus, the solutions are:

x=1+1112=1012=56x = \frac{-1 + 11}{12} = \frac{10}{12} = \frac{5}{6} x=11112=1212=1x = \frac{-1 - 11}{12} = \frac{-12}{12} = -1

Final Answer:

The zeros of the polynomial f(x)f(x) are: x=9,x=56,x=1x = 9, \quad x = \frac{5}{6}, \quad x = -1

Would you like more details or have any questions?

Here are five related questions to deepen understanding:

  1. How is synthetic division used to find the zeros of a polynomial?
  2. Why does the quadratic formula work for any quadratic equation?
  3. Can you perform synthetic division with complex numbers as roots?
  4. What are the conditions for a polynomial to have real versus complex roots?
  5. How can you check whether a given number is a zero of a polynomial without division?

Tip: Always verify your results by substituting the zeros back into the original polynomial to ensure the function equals zero at those points.

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Math Problem Analysis

Mathematical Concepts

Algebra
Polynomials
Synthetic Division
Quadratic Equations

Formulas

Quadratic formula: x = (-b ± √(b^2 - 4ac)) / 2a

Theorems

Remainder theorem
Factor theorem

Suitable Grade Level

Grades 10-12