Math Problem Statement

Use the vertex and intercepts to sketch the graph of the quadratic function. Give the equation for the​ parabola's axis of symmetry. Use the graph to determine the​ function's domain and range.

​f(x)equals=6 x squared plus 12 x minus 56x2+12x−5

Question content area bottom

Part 1

What is the​ vertex?

enter your response here

​(Type an ordered​ pair.)

Part 2

What are the​ x-intercepts?

enter your response here

​(Type an ordered pair. Use a comma to separate answers as needed. Round to the nearest hundredth as​ needed.)

Part 3

What is the​ y-intercept?

enter your response here

​(Type an ordered​ pair.)

Part 4

Graph the quadratic function. Choose the correct graph below.

A.

-55-2010xy

A coordinate system has a horizontal x-axis labeled from negative 5 to 5 in increments of 1 and a vertical y-axis labeled from negative 20 to 10 in increments of 2. A parabola that opens upward has vertex (1, negative 11) and passes through the y-axis at (0, negative 5).

B.

-55-1020xy

A coordinate system has a horizontal x-axis labeled from negative 5 to 5 in increments of 1 and a vertical y-axis labeled from negative 10 to 20 in increments of 2. A parabola that opens downward has vertex (1, 11) and passes through the y-axis at (0, 5).

C.

-55-1020xy

A coordinate system has a horizontal x-axis labeled from negative 5 to 5 in increments of 1 and a vertical y-axis labeled from negative 10 to 20 in increments of 2. A parabola that opens downward has vertex (negative 1,11) and passes through the y-axis at (0, 5).

Solution

To solve this question and provide answers for each part step-by-step:


Part 1: Find the vertex

The function is given as:
f(x)=6x2+12x5f(x) = 6x^2 + 12x - 5

The vertex form of a quadratic equation is:
f(x)=a(xh)2+kf(x) = a(x-h)^2 + k
where (h,k)(h, k) is the vertex.

To find the vertex, we use the formula for the x-coordinate of the vertex:
x=b2ax = -\frac{b}{2a}
Here, a=6a = 6, b=12b = 12, and c=5c = -5.

Substitute into the formula:
x=122(6)=1212=1x = -\frac{12}{2(6)} = -\frac{12}{12} = -1

Now substitute x=1x = -1 into the original function to find the y-coordinate (f(1)f(-1)):
f(1)=6(1)2+12(1)5f(-1) = 6(-1)^2 + 12(-1) - 5 f(1)=6(1)125=6125=11f(-1) = 6(1) - 12 - 5 = 6 - 12 - 5 = -11

Thus, the vertex is:
(1,11)\boxed{(-1, -11)}


Part 2: Find the x-intercepts

To find the x-intercepts, set f(x)=0f(x) = 0:
6x2+12x5=06x^2 + 12x - 5 = 0
This is a standard quadratic equation, so we solve using the quadratic formula:
x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
Substitute a=6a = 6, b=12b = 12, and c=5c = -5:
x=12±(12)24(6)(5)2(6)x = \frac{-12 \pm \sqrt{(12)^2 - 4(6)(-5)}}{2(6)} x=12±144+12012x = \frac{-12 \pm \sqrt{144 + 120}}{12} x=12±26412x = \frac{-12 \pm \sqrt{264}}{12} Simplify 264\sqrt{264}:
26416.25\sqrt{264} \approx 16.25 Now compute the two roots:
x=12+16.2512andx=1216.2512x = \frac{-12 + 16.25}{12} \quad \text{and} \quad x = \frac{-12 - 16.25}{12}

  1. First root:
    x=12+16.2512=4.25120.35x = \frac{-12 + 16.25}{12} = \frac{4.25}{12} \approx 0.35
  2. Second root:
    x=1216.2512=28.25122.35x = \frac{-12 - 16.25}{12} = \frac{-28.25}{12} \approx -2.35

Thus, the x-intercepts are approximately:
(0.35,0),(2.35,0)\boxed{(0.35, 0), (-2.35, 0)}


Part 3: Find the y-intercept

The y-intercept occurs when x=0x = 0. Substitute x=0x = 0 into f(x)f(x):
f(0)=6(0)2+12(0)5=5f(0) = 6(0)^2 + 12(0) - 5 = -5

Thus, the y-intercept is:
(0,5)\boxed{(0, -5)}


Part 4: Axis of symmetry

The axis of symmetry is the vertical line that passes through the vertex. Since the vertex is (1,11)(-1, -11), the axis of symmetry is:
x=1\boxed{x = -1}


Part 5: Domain and Range

  • Domain: Since this is a quadratic function, the domain is all real numbers:
    (,)\boxed{(-\infty, \infty)}

  • Range: The parabola opens upward (since a=6>0a = 6 > 0), so the minimum value of the function occurs at the vertex. The y-coordinate of the vertex is 11-11, so the range is:
    [11,)\boxed{[-11, \infty)}


Part 6: Correct graph

The parabola has:

  • Vertex: (1,11)(-1, -11)
  • Y-intercept: (0,5)(0, -5)
  • X-intercepts: (0.35,0)(0.35, 0) and (2.35,0)(-2.35, 0)

From the options provided, Graph A is correct because:

  • The parabola opens upward.
  • The vertex is (1,11)(-1, -11).
  • The y-intercept matches (0,5)(0, -5).

Final Answers:

  1. Vertex: (1,11)(-1, -11)
  2. X-intercepts: (0.35,0),(2.35,0)(0.35, 0), (-2.35, 0)
  3. Y-intercept: (0,5)(0, -5)
  4. Axis of symmetry: x=1x = -1
  5. Domain: (,)(-\infty, \infty)
  6. Range: [11,)[-11, \infty)

Relative Questions:

  1. What does the direction of the parabola depend on in a quadratic equation?
  2. How do you determine the vertex of a quadratic function from standard form?
  3. What role does the axis of symmetry play in graphing a parabola?
  4. How do you find the y-intercept of a function algebraically?
  5. How can you verify the solutions of a quadratic equation using a graphing tool?

Tip: The vertex is always the turning point of the parabola, and its x-coordinate can be found using x=b2ax = -\frac{b}{2a} for any quadratic in standard form.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Parabolas
Graphing

Formulas

x = -b / 2a (for vertex)
Quadratic formula: x = (-b ± √(b² - 4ac)) / 2a
f(x) = a(x - h)² + k (vertex form of a quadratic function)

Theorems

Quadratic formula
Vertex of a parabola

Suitable Grade Level

Grades 8-10