Big Ideas Math Algebra 1, 2015
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Big Ideas Math Algebra 1, 2015 View details
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Exercise 1 Page 473

Identify the vertex and the axis of symmetry of the parabola. Then make a table to find points on the curve.

Graph:

Comparison to the graph of f(x)=x^2: The graph of h is a vertical stretch by a factor of 2 and a vertical translation down 3 units of the graph of f.

Practice makes perfect
Let's start by recalling the vertex form of a quadratic function. f(x)=a(x- h)^2+k In this form the vertex of the parabola is the point ( h,k), and the axis of symmetry is the vertical line x= h. Now consider the given function.

h(x)=2x^2-3 ⇕ h(x)=2(x- 0)^2 + (- 3) We can see that h= 0 and that k=- 3. Therefore, the vertex is ( 0,- 3), and the axis of symmetry is x= 0. To graph the function we will make a table of values. Make sure to include x-values to the left and to the right of the axis of symmetry.

x 2x^2-3 h(x)=2x^2-3
- 2 2( - 2)^2-3 5
- 1 2( - 1)^2-3 - 1
1 2( 1)^2-3 - 1
2 2( 2)^2-3 5

Let's now draw the parabola that connects the obtained points and the vertex. We will also draw the axis of symmetry x=0, and the parent function f(x)=x^2.

From the graph above, we can note the following.

  • Both graphs open up.
  • Both graphs have the same axis of symmetry x=0.
  • The graph of the given function is narrower than the graph of the parent function.
  • The vertex of the given function, (0,- 3), is below the vertex of the parent function, (0,0).

From the graph and the observations above, we can conclude that the graph of h is a vertical stretch by a factor of 2 and a vertical translation down 3 units of the graph of f.