Math Problem Statement

Find all y-intercepts and x-intercepts of the graph of the function f(x) = 3x^3 + 3x^2 - 18x.

Solution

We are given the function:

f(x)=3x3+3x218xf(x) = 3x^3 + 3x^2 - 18x

1. Finding the y-intercept:

The y-intercept occurs when x=0x = 0. So, let's calculate f(0)f(0):

f(0)=3(0)3+3(0)218(0)=0f(0) = 3(0)^3 + 3(0)^2 - 18(0) = 0

Thus, the y-intercept is at the point (0,0)(0, 0).

2. Finding the x-intercepts:

The x-intercepts occur where f(x)=0f(x) = 0. We need to solve the equation:

3x3+3x218x=03x^3 + 3x^2 - 18x = 0

Factor out the common term, which is 3x3x:

3x(x2+x6)=03x(x^2 + x - 6) = 0

Now, solve x2+x6=0x^2 + x - 6 = 0. This is a quadratic equation, which we can factor:

x2+x6=(x2)(x+3)x^2 + x - 6 = (x - 2)(x + 3)

Thus, the factored form of the equation is:

3x(x2)(x+3)=03x(x - 2)(x + 3) = 0

Now, solve for xx:

x=0,x=2,x=3x = 0, \quad x = 2, \quad x = -3

So, the x-intercepts are at the points (0,0)(0, 0), (2,0)(2, 0), and (3,0)(-3, 0).

Summary:

  • The y-intercept is at (0,0)(0, 0).
  • The x-intercepts are at (0,0)(0, 0), (2,0)(2, 0), and (3,0)(-3, 0).

Would you like further details on any part of this process?

Here are 5 related questions to explore further:

  1. How do we determine if a graph crosses or touches the x-axis at the intercepts?
  2. How does factoring help in solving cubic equations?
  3. Can we use the quadratic formula instead of factoring in this case?
  4. How does the behavior of the graph change near each intercept?
  5. What are the steps to check for symmetry in the graph of this function?

Tip: When solving cubic functions, always check for common factors to simplify the equation first.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Algebra
Factoring Polynomials
Intercepts

Formulas

f(x) = ax^3 + bx^2 + cx
Factoring Quadratic Equations

Theorems

Zero Product Property

Suitable Grade Level

Grades 10-12