Which is one of the transformations applied to the graph of $f(x)=x^2$ to change it into the graph of $g(x)=-x^2+16x-44$?


AThe graph of $f(x)=x^2$ is shifted left
BThe graph of $f(x)=x^2$ is shifted right
CThe graph of $f(x)=x^2$ is shifted down
DThe graph of $f(x)=x^2$ is reflected over the x-axis

Verified Answer :

  • Factor out the leading coefficient and complete the square for \(g(x) = -x^2 + 16x - 44\).
  • Rewrite \(g(x)\) in vertex form: \(g(x) = -(x - 8)^2 + 20\).
  • Identify the transformations by comparing to \(f(x) = x^2\): reflection over the x-axis, horizontal shift of 8 units right, and vertical shift of 20 units up.
  • The transformations are: \(\boxed{\text{reflected over the x-axis, shifted 8 units to the right, shifted 20 units up}}\).

Explanation

  1. Analyzing the Functions

To determine the transformations applied to the graph of \(f(x) = x^2\) to obtain the graph of \(g(x) = -x^2 + 16x - 44\), we first write the function \(g(x)\) in vertex form. The vertex form of a quadratic function is given by \(g(x) = a(x - h)^2 + k\), where \((h, k)\) is the vertex of the parabola. This form allows us to easily identify horizontal and vertical shifts as well as reflections.

  1. Completing the Square

We start with \(g(x) = -x^2 + 16x - 44\). First, factor out the coefficient of the \(x^2\) term, which is -1, to group the \(x\)-terms:
\[g(x) = -(x^2 - 16x) - 44.\]
To complete the square for the expression inside the parentheses, we take half of the coefficient of \(x\), which is \(-16/2 = -8\), and square it: \((-8)^2 = 64\). We add and subtract 64 inside the parentheses:
\[g(x) = -(x^2 - 16x + 64 - 64) - 44.\]
Distribute the -1 to the -64 to move it outside the parentheses:
\[g(x) = -(x^2 - 16x + 64) + 64 - 44.\]
Simplify the expression to obtain:
\[g(x) = -(x - 8)^2 + 20.\]

  1. Identifying the Transformations

Now, we compare the transformed function \(g(x) = -(x - 8)^2 + 20\) to the original function \(f(x) = x^2\).

  1. The negative sign in front of the \((x-8)^2\) term indicates a reflection over the x-axis.
  2. The \((x - 8)\) term indicates a horizontal translation of 8 units to the right.
  3. The \(+ 20\) constant indicates a vertical translation of 20 units up.

Thus, the transformations are a reflection over the x-axis, a horizontal shift of 8 units to the right, and a vertical shift of 20 units up. Any one of these can be identified as a transformation.

Examples

In architecture or engineering, understanding transformations is key to designing structures like parabolic arches. If you have a basic arch design modeled by \(f(x) = x^2\), you can adjust its position and orientation using these shifts and reflections to perfectly fit a structure's dimensions. For example, if you need to place a foundation arc that is reflected and shifted to support a specific entryway, calculating these exact transformations ensures the design is structurally sound and aesthetically centered.