Math Problem Statement

f(x)=3x^2-x-2 ​(a) Is the point (-1,2) on the graph of​ f? ​(b) If x​ = 2​, what is​ f(x)? What point is on the graph of​ f? ​(c) If​ f(x) = negative 2​, what is​ x? What​ point(s) is/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

Let's address each part of the question one by one for the function f(x)=3x2x2f(x) = 3x^2 - x - 2.

(a) Is the point (1,2)(-1, 2) on the graph of ff?

To determine if the point (1,2)(-1, 2) is on the graph, substitute x=1x = -1 into the function and see if f(1)=2f(-1) = 2:

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

Since f(1)=2f(-1) = 2, the point (1,2)(-1, 2) is indeed on the graph of f(x)f(x).

(b) If x=2x = 2, what is f(x)f(x)? What point is on the graph of ff?

Substitute x=2x = 2 into the function:

f(2)=3(2)222=3(4)22=1222=8f(2) = 3(2)^2 - 2 - 2 = 3(4) - 2 - 2 = 12 - 2 - 2 = 8

So, f(2)=8f(2) = 8. The point (2,8)(2, 8) is on the graph of f(x)f(x).

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

Set f(x)=2f(x) = -2 and solve for xx:

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

Adding 2 to both sides:

3x2x=03x^2 - x = 0

Factor the equation:

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

So, x=0x = 0 or x=13x = \frac{1}{3}.

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

(d) What is the domain of ff?

The domain of a quadratic function is all real numbers since there are no restrictions on the values that xx can take. Thus, the domain of f(x)f(x) is (,)(-\infty, \infty).

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

To find the xx-intercepts, set f(x)=0f(x) = 0 and solve for xx:

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

Use the quadratic formula:

x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Where a=3a = 3, b=1b = -1, and c=2c = -2:

x=(1)±(1)24(3)(2)2(3)x = \frac{-(-1) \pm \sqrt{(-1)^2 - 4(3)(-2)}}{2(3)}

x=1±1+246=1±256=1±56x = \frac{1 \pm \sqrt{1 + 24}}{6} = \frac{1 \pm \sqrt{25}}{6} = \frac{1 \pm 5}{6}

So:

x=66=1orx=46=23x = \frac{6}{6} = 1 \quad \text{or} \quad x = \frac{-4}{6} = -\frac{2}{3}

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.

To find the yy-intercept, set x=0x = 0 and solve for f(0)f(0):

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

The yy-intercept is (0,2)(0, -2).


Would you like more details or have any questions? Here are some related questions you might find interesting:

  1. How do you determine the vertex of the quadratic function f(x)=3x2x2f(x) = 3x^2 - x - 2?
  2. What is the axis of symmetry for the function f(x)=3x2x2f(x) = 3x^2 - x - 2?
  3. How do you graph the function f(x)=3x2x2f(x) = 3x^2 - x - 2?
  4. What are the maximum and minimum values of the function f(x)=3x2x2f(x) = 3x^2 - x - 2?
  5. How does changing the coefficients of x2x^2, xx, and the constant term affect the shape and position of the parabola?

Tip: When solving quadratic equations, always check if they can be factored easily before using the quadratic formula—it can save time!

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Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Graphing
Intercepts
Domain

Formulas

Quadratic formula

Theorems

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Suitable Grade Level

Grades 9-12