Skip to main content
Ch. 3 - Polynomial and Rational Functions
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063Not the one you use?Change textbook
Chapter 4, Problem 39

Graph each polynomial function. Factor first if the polynomial is not in factored form. ƒ(x)=-x3+x2+2x

Verified step by step guidance
1
Start by writing down the given polynomial function: \(f(x) = -x^3 + x^2 + 2x\).
Factor the polynomial by first factoring out the greatest common factor (GCF). Identify the GCF of all terms, which is \(-x\), and factor it out: \(f(x) = -x(x^2 - x - 2)\).
Next, factor the quadratic expression inside the parentheses: \(x^2 - x - 2\). Find two numbers that multiply to \(-2\) and add to \(-1\). These numbers are \(-2\) and \(1\), so factor as \((x - 2)(x + 1)\).
Rewrite the fully factored form of the polynomial as \(f(x) = -x(x - 2)(x + 1)\).
Use the factored form to find the roots of the function by setting each factor equal to zero: \(-x = 0\), \(x - 2 = 0\), and \(x + 1 = 0\). These roots will help you plot the x-intercepts on the graph.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
8m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Polynomial Functions

A polynomial function is an expression consisting of variables raised to whole-number exponents and coefficients combined using addition, subtraction, and multiplication. Understanding the degree and leading coefficient helps predict the general shape and end behavior of the graph.
Recommended video:
06:04
Introduction to Polynomial Functions

Factoring Polynomials

Factoring involves rewriting a polynomial as a product of simpler polynomials or factors. This process helps identify the roots or zeros of the function, which correspond to the x-intercepts on the graph, making it easier to sketch the function accurately.
Recommended video:
Guided course
07:30
Introduction to Factoring Polynomials

Graphing Polynomial Functions

Graphing involves plotting key points such as zeros, intercepts, and turning points, and understanding the end behavior based on the degree and leading coefficient. Factoring aids in finding zeros, while evaluating the function at various points helps shape the curve.
Recommended video:
05:25
Graphing Polynomial Functions