Math Problem Statement

The polynomial of degree 4, P(x), has a root of multiplicity 2 at x = 2 and roots of multiplicity 1 at x = 0 and x = -4. It goes through the point (5, 243). Find a formula for P(x).

Solution

The given problem asks for a polynomial P(x)P(x) of degree 4 with the following conditions:

  • It has a root of multiplicity 2 at x=2x = 2.
  • It has roots of multiplicity 1 at x=0x = 0 and x=4x = -4.
  • It passes through the point (5,243)(5, 243).

Step-by-Step Solution:

  1. General Form of the Polynomial:
    Since the root at x=2x = 2 has multiplicity 2, the factor associated with it is (x2)2(x - 2)^2.
    The roots at x=0x = 0 and x=4x = -4 have multiplicity 1, so their factors are xx and (x+4)(x + 4), respectively.

    Therefore, the polynomial can be written in the form: P(x)=a(x2)2x(x+4)P(x) = a(x - 2)^2 x (x + 4) where aa is a constant to be determined.

  2. Using the Point (5,243)(5, 243):
    The polynomial passes through the point (5,243)(5, 243), so we can use this information to solve for aa.
    Substituting x=5x = 5 and P(x)=243P(x) = 243 into the equation: 243=a(52)2(5)(5+4)243 = a(5 - 2)^2 (5)(5 + 4) Simplifying: 243=a(3)2(5)(9)243 = a(3)^2 (5)(9) 243=a(9)(5)(9)243 = a(9)(5)(9) 243=a×405243 = a \times 405 Solving for aa: a=243405=915=35a = \frac{243}{405} = \frac{9}{15} = \frac{3}{5}

  3. Final Polynomial:
    Substituting a=35a = \frac{3}{5} back into the general form of the polynomial: P(x)=35(x2)2x(x+4)P(x) = \frac{3}{5}(x - 2)^2 x (x + 4)

Final Answer:

P(x)=35(x2)2x(x+4)P(x) = \frac{3}{5}(x - 2)^2 x (x + 4)

Let me know if you'd like more details or further clarifications!


Here are five related questions that expand on this topic:

  1. How do you determine the degree of a polynomial from its roots and multiplicities?
  2. What is the significance of multiplicity in polynomial roots?
  3. How does passing through a specific point help in finding the leading coefficient?
  4. How can we check if a polynomial matches certain given conditions?
  5. Can the process change if a polynomial is factored over complex numbers?

Tip: When working with polynomial roots and multiplicities, always pay attention to how each root affects the shape and behavior of the graph at that point!

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Math Problem Analysis

Mathematical Concepts

Polynomials
Roots
Multiplicity

Formulas

P(x) = a(x - 2)^2 * x * (x + 4)

Theorems

Multiplicity of Roots Theorem

Suitable Grade Level

Grades 10-12