Skip to main content
Ch. 3 - Polynomial and Rational Functions
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 4, Problem 55

Write an equation in vertex form of the parabola that has the same shape as the graph of f(x) = 3x2 or g(x) = -3x2, but with the given maximum or minimum. Minimum = 0 at x = 11

Verified step by step guidance
1
Identify the given information: the parabola has the same shape as either \(f(x) = 3x^{2}\) or \(g(x) = -3x^{2}\), and it has a minimum value of 0 at \(x = 11\).
Since the parabola has a minimum, it opens upwards, so the coefficient of \(x^{2}\) is positive. This means the shape corresponds to \(f(x) = 3x^{2}\), where the leading coefficient \(a = 3\).
Recall the vertex form of a parabola: \(y = a(x - h)^{2} + k\), where \((h, k)\) is the vertex of the parabola.
Use the vertex coordinates given: \(h = 11\) and \(k = 0\), and substitute \(a = 3\) into the vertex form to get the equation.
Write the equation as \(y = 3(x - 11)^{2} + 0\), which simplifies to \(y = 3(x - 11)^{2}\).

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
1m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Vertex Form of a Quadratic Function

The vertex form of a quadratic function is expressed as f(x) = a(x - h)^2 + k, where (h, k) is the vertex of the parabola. This form makes it easy to identify the maximum or minimum point and the parabola's shape. The value of 'a' determines the direction and width of the parabola.
Recommended video:
08:07
Vertex Form

Effect of the Coefficient 'a' on Parabola Shape

The coefficient 'a' in a quadratic function affects the parabola's opening direction and steepness. If 'a' is positive, the parabola opens upward with a minimum vertex; if negative, it opens downward with a maximum vertex. The absolute value of 'a' controls how narrow or wide the parabola appears.
Recommended video:
5:28
Horizontal Parabolas

Using Vertex Coordinates to Write the Equation

Given the vertex coordinates (h, k), you can write the quadratic equation in vertex form by substituting h and k into f(x) = a(x - h)^2 + k. This allows you to create a parabola with a specific maximum or minimum at a given point, matching the shape defined by the coefficient 'a'.
Recommended video:
5:47
Solving Exponential Equations Using Logs