McGraw Hill Integrated II, 2012
MH
McGraw Hill Integrated II, 2012 View details
Mid-Chapter Quiz
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Exercise 22 Page 132

Transform the graph of the parent function y=x^2 so it matches the given graph.

D

We want to describe how to transform the parent function y=x^2 to the given graph. To do so, we need to consider four possible transformations.

  1. Reflections
  2. Stretches and compressions
  3. Horizontal translations
  4. Vertical translations

Notice that we only need to consider the first, second, and fourth transformations.

Reflection

Whenever x^2 is multiplied by a negative number, we will start by reflecting the graph across the x-axis.

Note how each x-coordinate stays the same and how each y-coordinate changes its sign.

Stretch or Compression

We have a vertical stretch when x^2 is multiplied by a number whose absolute value is greater than one. If x^2 is multiplied by a number whose absolute value is less than one, a vertical compression will take place.
If x^2 is being multiplied by a negative number, the above still applies but everything will be upside down. In the given exercise, notice that the given graph is stretched vertically. x^2 is multiplied by -2. Therefore, the previous graph will be vertically stretched by a factor of 2.

Vertical Translation

If an addition or subtraction is applied to the whole function, the graph will be vertically translated. In the case of addition, the graph will be translated up. In the case of subtraction, it will be moved downwards. In the given exercise, the graph is translated one unit up compared to the previous graph.

Final Graph

Let's now graph the given function and the parent function y=x^2 on the same coordinate grid.

Finally, let's summarize how to draw the graph of the given function when starting with the parent function, y=x^2.

  • Reflection across the x-axis
  • Vertical stretch by a scale factor of 2
  • Translation one unit up

Therefore the function we are looking for is y=-2x^2+1, and the correct answer is D.