Big Ideas Math Integrated III
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Big Ideas Math Integrated III View details
5. Transformations of Quadratic Functions
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Exercise 2 Page 73

Consider vertical translations, horizontal translations, and vertical stretches and shrinks.

Supposing that a, h, and k are positive numbers, g(x)=a(x-h)^2+k is a translation h units right, vertical stretch or shrink with factor a, followed by a translation k units up of the parent function f(x)=x^2. See solution for negative values of a, h, or k.

Practice makes perfect
We want to determine how the constants a, h, and k affect the graph of the quadratic function g(x)=a(x-h)^2+k. To do so, let's look at the possible transformations. Then we can more clearly identify the ones being applied to the parent function f(x)=x^2.
Transformations of f(x)=x^2
Vertical Translations Translation up k units, k>0 y=x^2+ k
Translation down k units, k>0 y=x^2- k
Horizontal Translations Translation right h units, h>0 y=(x- h)^2
Translation left h units, h>0 y=(x+ h)^2
Vertical Stretch or Shrink Vertical stretch, a>1 y= ax^2
Vertical shrink, 0< a< 1 y= ax^2
Reflections In the x-axis y=- x^2
In the y-axis y=(- x)^2

Let's suppose that a, h, and k are positive numbers. We conclude from the table that g(x)=a(x-h)^2+k is a translation h units right, vertical stretch or shrink with factor a, followed by a translation k units up of the parent function f(x)=x^2. What happens if a, h, or k are negative?

  • If h<0, the horizontal translation is done to the left.
  • If k<0, the vertical translation is done downwards.
  • If a<0, after the stretch or shrink a reflection in the x-axis takes place.