Math Problem Statement

Write an equation for a polynomial function whose graph intersects the horizontal axis at -14, -5, and 4 and has a vertical intercept at (0, -56).

Solution

The problem asks to find the equation of a polynomial function with specific properties:

  • The graph intersects the horizontal axis at x=14x = -14, x=5x = -5, and x=4x = 4. These are the x-intercepts of the polynomial, meaning the roots of the equation.
  • It has a vertical intercept at (0,56)(0, -56), meaning the value of the polynomial at x=0x = 0 is 56-56.

The general form of a polynomial with roots x=14x = -14, x=5x = -5, and x=4x = 4 can be written as: f(x)=a(x+14)(x+5)(x4)f(x) = a(x + 14)(x + 5)(x - 4) where aa is a constant that will be determined by the vertical intercept.

To find aa, we substitute x=0x = 0 and f(0)=56f(0) = -56: 56=a(0+14)(0+5)(04)-56 = a(0 + 14)(0 + 5)(0 - 4) 56=a(14)(5)(4)-56 = a(14)(5)(-4) 56=a(280)-56 = a(-280) a=56280=0.2a = \frac{-56}{-280} = 0.2

Thus, the equation of the polynomial is: f(x)=0.2(x+14)(x+5)(x4)f(x) = 0.2(x + 14)(x + 5)(x - 4)

This corresponds to the third option in the given choices:

  • 0.2(x+14)(x+5)(x4)0.2(x + 14)(x + 5)(x - 4)

Would you like more details on this, or have any questions?


Here are five related questions:

  1. How do you find the degree of a polynomial given its roots?
  2. What is the significance of the constant aa in the polynomial equation?
  3. How do you determine the x-intercepts of a polynomial from its equation?
  4. How does the value of f(0)f(0) determine the vertical intercept?
  5. Can a polynomial have multiple vertical intercepts?

Tip: Always use the x-intercepts to directly construct the factors of a polynomial equation, and then adjust the constant based on any given additional points.

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Math Problem Analysis

Mathematical Concepts

Polynomial Functions
X-Intercepts
Vertical Intercept

Formulas

f(x) = a(x - r1)(x - r2)(x - r3)

Theorems

Factor Theorem

Suitable Grade Level

Grades 9-12