Math Problem Statement

Use the quadratic function f(x) = x^2 - 4x - 60 to answer the following: a) Determine the vertex. b) Does the graph "open up" or "open down"? c) What is the equation of the axis of symmetry? d) Find any x-intercepts. e) Find the y-intercept. g) State the domain and range in interval notation.

Solution

Let's work through the given problem, which involves analyzing the quadratic function f(x)=x24x60f(x) = x^2 - 4x - 60. I'll address each part one by one:

a) Determine the vertex.

The vertex of a parabola given by f(x)=ax2+bx+cf(x) = ax^2 + bx + c can be found using the formula: x=b2ax = -\frac{b}{2a} Here, a=1a = 1 and b=4b = -4, so: x=421=42=2x = -\frac{-4}{2 \cdot 1} = \frac{4}{2} = 2 To find the y-coordinate of the vertex, substitute x=2x = 2 into the function: f(2)=(2)24(2)60=4860=64f(2) = (2)^2 - 4(2) - 60 = 4 - 8 - 60 = -64 So, the vertex is (2,64)(2, -64).

b) Does the graph "open up" or "open down"?

The graph of a quadratic function f(x)=ax2+bx+cf(x) = ax^2 + bx + c opens upward if a>0a > 0 and downward if a<0a < 0. Here, a=1a = 1, which is positive, so the graph opens upward.

c) What is the equation of the axis of symmetry?

The axis of symmetry can be found from the x-coordinate of the vertex: x=2x = 2 So, the equation of the axis of symmetry is x=2x = 2.

d) Find any x-intercepts.

To find the x-intercepts, set f(x)=0f(x) = 0: x24x60=0x^2 - 4x - 60 = 0 This is a quadratic equation that we can solve using the quadratic formula: x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} Substitute a=1a = 1, b=4b = -4, and c=60c = -60: x=(4)±(4)241(60)21x = \frac{-(-4) \pm \sqrt{(-4)^2 - 4 \cdot 1 \cdot (-60)}}{2 \cdot 1} x=4±16+2402x = \frac{4 \pm \sqrt{16 + 240}}{2} x=4±2562x = \frac{4 \pm \sqrt{256}}{2} x=4±162x = \frac{4 \pm 16}{2} So, the solutions are: x=4+162=10andx=4162=6x = \frac{4 + 16}{2} = 10 \quad \text{and} \quad x = \frac{4 - 16}{2} = -6 The x-intercepts are (10,0)(10, 0) and (6,0)(-6, 0).

e) Find the y-intercept.

The y-intercept occurs when x=0x = 0: f(0)=024(0)60=60f(0) = 0^2 - 4(0) - 60 = -60 So, the y-intercept is (0,60)(0, -60).

g) State the domain and range in interval notation.

  • The domain of a quadratic function is all real numbers: Domain: (,)\text{Domain: } (-\infty, \infty)
  • Since the parabola opens upward and has a vertex at (2,64)(2, -64), the range is: Range: [64,)\text{Range: } [-64, \infty)

Summary of Answers:

  • a) Vertex: (2,64)(2, -64)
  • b) The graph opens upward.
  • c) Axis of symmetry: x=2x = 2
  • d) X-intercepts: (10,0)(10, 0) and (6,0)(-6, 0)
  • e) Y-intercept: (0,60)(0, -60)
  • g) Domain: (,)(-\infty, \infty), Range: [64,)[-64, \infty)

Would you like more details or have any questions on these solutions? Here are five related questions that might be helpful to explore:

  1. How do you derive the formula for the vertex of a parabola?
  2. Why does the sign of aa determine whether a parabola opens up or down?
  3. What is the relationship between the vertex and the axis of symmetry?
  4. How can the discriminant b24acb^2 - 4ac help determine the number of x-intercepts?
  5. How do you graph a quadratic function step-by-step?

Tip: When solving quadratic equations, the quadratic formula is useful for finding exact solutions, especially when the factors aren't obvious.

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Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Vertex Form
Intercepts
Graphing Parabolas
Domain and Range

Formulas

Vertex formula: x = -b / (2a)
Quadratic formula: x = (-b ± sqrt(b^2 - 4ac)) / 2a

Theorems

Axis of symmetry theorem: x = -b / (2a)
Quadratic formula

Suitable Grade Level

Grades 9-12