Math Problem Statement

Consider the parabola given by the equation: f(x)=4x2+14x-14

Find the following for this parabola:

A) The vertex:   

B) The vertical intercept is the point   

C) Find the coordinates of the two x intercepts of the parabola and write them as a list, separated by commas:    It is OK to round your value(s) to to two decimal places.

Solution

To solve the given parabola equation f(x)=4x2+14x14f(x) = 4x^2 + 14x - 14, we'll follow the steps for each part of the question:

A) The Vertex:

The vertex of a parabola in the form f(x)=ax2+bx+cf(x) = ax^2 + bx + c can be found using the formula for the x-coordinate of the vertex:

xvertex=b2ax_{\text{vertex}} = -\frac{b}{2a}

For the given equation, a=4a = 4, b=14b = 14, and c=14c = -14.

xvertex=142(4)=148=1.75x_{\text{vertex}} = -\frac{14}{2(4)} = -\frac{14}{8} = -1.75

Now, substitute x=1.75x = -1.75 into the original equation to find the y-coordinate of the vertex:

f(1.75)=4(1.75)2+14(1.75)14f(-1.75) = 4(-1.75)^2 + 14(-1.75) - 14 f(1.75)=4(3.0625)+14(1.75)14f(-1.75) = 4(3.0625) + 14(-1.75) - 14 f(1.75)=12.2524.514=26.25f(-1.75) = 12.25 - 24.5 - 14 = -26.25

Thus, the vertex is:

(1.75,26.25)\boxed{(-1.75, -26.25)}

B) The Vertical Intercept:

The vertical intercept (also called the y-intercept) is the point where the parabola crosses the y-axis, which occurs when x=0x = 0.

Substitute x=0x = 0 into the equation:

f(0)=4(0)2+14(0)14=14f(0) = 4(0)^2 + 14(0) - 14 = -14

So, the vertical intercept is:

(0,14)\boxed{(0, -14)}

C) The x-Intercepts:

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

4x2+14x14=04x^2 + 14x - 14 = 0

We can solve this using the quadratic formula, x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}, where a=4a = 4, b=14b = 14, and c=14c = -14.

First, calculate the discriminant:

Δ=b24ac=1424(4)(14)=196+224=420\Delta = b^2 - 4ac = 14^2 - 4(4)(-14) = 196 + 224 = 420

Now, apply the quadratic formula:

x=14±4202(4)=14±4208x = \frac{-14 \pm \sqrt{420}}{2(4)} = \frac{-14 \pm \sqrt{420}}{8}

The square root of 420 is approximately 20.4920.49. Thus, we get two solutions:

x1=14+20.498=6.4980.81x_1 = \frac{-14 + 20.49}{8} = \frac{6.49}{8} \approx 0.81 x2=1420.498=34.4984.31x_2 = \frac{-14 - 20.49}{8} = \frac{-34.49}{8} \approx -4.31

So, the x-intercepts are approximately:

(0.81,0),(4.31,0)\boxed{(0.81, 0), (-4.31, 0)}

Summary:

  • A) Vertex: (1.75,26.25)(-1.75, -26.25)
  • B) Vertical Intercept: (0,14)(0, -14)
  • C) X-Intercepts: 0.81,4.310.81, -4.31

Would you like more details or have any questions?

Here are 5 follow-up questions to extend this topic:

  1. How do you find the focus and directrix of a parabola?
  2. Can you explain the role of the discriminant in determining the number of real solutions for x-intercepts?
  3. What is the axis of symmetry for the parabola in this case?
  4. How would the graph of the parabola change if the coefficient of x2x^2 were negative?
  5. Can you derive the vertex form of the quadratic equation from its standard form?

Tip: The axis of symmetry of a parabola always passes through its vertex and has the equation x=b2ax = \frac{-b}{2a}.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Parabolas
Intercepts

Formulas

Vertex formula: x = -b / (2a)
Quadratic equation: ax^2 + bx + c = 0
Quadratic formula: x = (-b ± √(b^2 - 4ac)) / 2a

Theorems

Quadratic Formula
Symmetry of Parabolas

Suitable Grade Level

Grades 9-10