Math Problem Statement

Answer the questions about the following function. f left parenthesis x right parenthesis equals 3 x squared minus x minus 2 ​(a) Is the point left parenthesis 2 comma 8 right parenthesis on the graph of​ f? ​(b) If x​ = negative 1​, what is​ f(x)? What point is on the graph of​ f? ​(c) If​ f(x) = negative 2​, what is​ x? What​ point(s) are on the graph of​ f? ​(d) What is the domain of​ f? ​(e) List the​ x-intercept(s), if​ any, of the graph of f. ​(f) List the​ y-intercept, if there is​ one, of the graph of f.

Solution

Given the function f(x)=3x2x2f(x) = 3x^2 - x - 2, let's answer each question step by step:

(a) Is the point (2,8)(2, 8) on the graph of ff?

To check if the point (2,8)(2, 8) is on the graph, we need to evaluate f(2)f(2) and see if the result equals 8.

f(2)=3(2)2(2)2=3(4)22=1222=8f(2) = 3(2)^2 - (2) - 2 = 3(4) - 2 - 2 = 12 - 2 - 2 = 8

Since f(2)=8f(2) = 8, the point (2,8)(2, 8) is indeed on the graph of ff.

(b) If x=1x = -1, what is f(x)f(x)? What point is on the graph of ff?

We need to calculate f(1)f(-1):

f(1)=3(1)2(1)2=3(1)+12=3+12=2f(-1) = 3(-1)^2 - (-1) - 2 = 3(1) + 1 - 2 = 3 + 1 - 2 = 2

So, f(1)=2f(-1) = 2, which means the point (1,2)(-1, 2) is on the graph of ff.

(c) If f(x)=2f(x) = -2, what is xx? What point(s) are on the graph of ff?

We solve for xx when f(x)=2f(x) = -2:

3x2x2=23x^2 - x - 2 = -2

Add 2 to both sides:

3x2x=03x^2 - x = 0

Factor the equation:

x(3x1)=0x(3x - 1) = 0

So, x=0x = 0 or 3x1=03x - 1 = 0, which gives x=13x = \frac{1}{3}.

Thus, the points (0,2)(0, -2) and (13,2)\left( \frac{1}{3}, -2 \right) are on the graph of ff.

(d) What is the domain of ff?

The function f(x)=3x2x2f(x) = 3x^2 - x - 2 is a polynomial, and polynomials are defined for all real numbers. Therefore, the domain of ff is:

Domain of f=(,)\text{Domain of } f = (-\infty, \infty)

(e) List the xx-intercept(s), if any, of the graph of ff.

The xx-intercepts occur when f(x)=0f(x) = 0:

3x2x2=03x^2 - x - 2 = 0

We solve this quadratic equation using the quadratic formula:

x=(1)±(1)24(3)(2)2(3)=1±1+246=1±256=1±56x = \frac{-(-1) \pm \sqrt{(-1)^2 - 4(3)(-2)}}{2(3)} = \frac{1 \pm \sqrt{1 + 24}}{6} = \frac{1 \pm \sqrt{25}}{6} = \frac{1 \pm 5}{6}

This gives two solutions:

x=1+56=1andx=156=23x = \frac{1 + 5}{6} = 1 \quad \text{and} \quad x = \frac{1 - 5}{6} = -\frac{2}{3}

Therefore, the xx-intercepts are (1,0)(1, 0) and (23,0)\left( -\frac{2}{3}, 0 \right).

(f) List the yy-intercept, if there is one, of the graph of ff.

The yy-intercept occurs when x=0x = 0:

f(0)=3(0)202=2f(0) = 3(0)^2 - 0 - 2 = -2

So, the yy-intercept is (0,2)(0, -2).


Do you want more details on any step? Here are five related questions you might want to explore:

  1. What is the vertex of the function f(x)=3x2x2f(x) = 3x^2 - x - 2?
  2. How would you find the axis of symmetry for this quadratic function?
  3. What is the range of the function f(x)=3x2x2f(x) = 3x^2 - x - 2?
  4. Can you sketch the graph of the function using the points we found?
  5. What is the behavior of f(x)f(x) as xx \to \infty and xx \to -\infty?

Tip: For quadratic functions, the vertex can be found using the formula x=b2ax = -\frac{b}{2a}, where aa and bb come from the standard form ax2+bx+cax^2 + bx + c.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Functions
Graphing
Domain and Range

Formulas

Quadratic formula: x = (-b ± √(b² - 4ac)) / 2a
Standard form of quadratic: f(x) = ax² + bx + c

Theorems

Quadratic Formula Theorem
Intercepts of Functions

Suitable Grade Level

Grades 9-11