Math Problem Statement

One root of f (x) = x cubed minus 9 x squared + 26 x minus 24 is x = 2. What are all the roots of the function? Use the Remainder Theorem. x = 2, x = 3, or x = 4 x = –2, x = –3, or x = –4 x = 1, x = 2, x = 3, or x = 13 x = –1, x = –2, x = –3, or x =

Solution

We are tasked with finding all the roots of the polynomial f(x)=x39x2+26x24f(x) = x^3 - 9x^2 + 26x - 24, given that x=2x = 2 is one of its roots. Let's solve this using the Remainder Theorem and synthetic division.


Step 1: Verify that x=2x = 2 is a root

The Remainder Theorem states that if x=2x = 2 is a root, substituting x=2x = 2 into f(x)f(x) will yield f(2)=0f(2) = 0. Let us verify this:

f(2)=239(22)+26(2)24f(2) = 2^3 - 9(2^2) + 26(2) - 24 =836+5224=0= 8 - 36 + 52 - 24 = 0

Since f(2)=0f(2) = 0, x=2x = 2 is indeed a root.


Step 2: Perform synthetic division by x2x - 2

Divide f(x)f(x) by x2x - 2 using synthetic division:

Polynomial: f(x)=x39x2+26x24f(x) = x^3 - 9x^2 + 26x - 24

  • Coefficients: [1,9,26,24][1, -9, 26, -24]
  • Divisor root: x=2x = 2

Perform the division:

2 & 1 & -9 & 26 & -24 \\ & & 2 & -14 & 24 \\ \hline & 1 & -7 & 12 & 0 \\ \end{array}$$ The quotient is $$x^2 - 7x + 12$$, and the remainder is $$0$$, confirming that $$x - 2$$ divides $$f(x)$$ completely. --- ### Step 3: Factor the quotient $$x^2 - 7x + 12$$ The quadratic $$x^2 - 7x + 12$$ can be factored easily: $$x^2 - 7x + 12 = (x - 3)(x - 4)$$ --- ### Step 4: Combine all roots The complete factorization of $$f(x)$$ is: $$f(x) = (x - 2)(x - 3)(x - 4)$$ Thus, the roots of $$f(x)$$ are: $$x = 2, \, x = 3, \, x = 4$$ --- ### Final Answer: The correct choice is: $$\boxed{x = 2, \, x = 3, \, x = 4}$$ --- Would you like a detailed explanation of synthetic division or factoring? ### Related Questions: 1. How does the Remainder Theorem help verify roots of polynomials? 2. Can all cubic equations be solved using synthetic division? 3. How do you determine if a quadratic factor has real roots? 4. Why is $$x = 2$$ called a "root" of the function $$f(x)$$? 5. How can we use the Rational Root Theorem to find roots systematically? ### Tip: For polynomials of degree 3 or higher, always try to simplify using known roots and synthetic division to reduce the degree!

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Math Problem Analysis

Mathematical Concepts

Polynomials
Roots of Functions
Synthetic Division

Formulas

Polynomial Division: f(x) = (x - c)q(x) + r
Factorization of Quadratics: ax^2 + bx + c = (x - p)(x - q)

Theorems

Remainder Theorem
Fundamental Theorem of Algebra

Suitable Grade Level

Grades 9-12