Guided Practice #2

Practice Problem #2

Determine the vertex of the function f(x) = -4x2 - 16x + 2.

Why Always remember that f(x) can always be used in place of y. They both have the same meaning. did the example use f(x) instead of y?

Using the formula x = [-b]/[2a] , find the x-coordinate of the vertex.

Substitute for b = -16 and a =-4. The negative on the outside must remain outside the parentheses.

x = [-()]/[2()]

Simplify the numerator and denominator.

x = 16/-8

x = ___

You just found the x-coordinate to be x = -2. Substitute this value into the original equation to find the y-coordiante.

f(x) = -4(-2)2 - 16(-2) + 2

Simplify using the order of operations.

y = -4( ___ ) + ___ + 2

Simplify using the order of operations.

y = ___ + 32 + 2

Simplify using the order of operations.

y = ___

You found that x = -2 and y = 18. What is the vertex of your parabola?

( ___, ___ )

Practice Problem #3

Describe how the graph of y = -x2 + 4x + 4 was obtained from the parent graph y = x2.

  1. The graph was reflected over the x-axis, shifted left 2 units and up 8 units.
  2. The graph of x2 was shifted left 2 units and up 8 units.
  3. The graph was reflected over the x-axis, shifted right 2 units and up 8 units.

Practice Problem #4

Describe how the graph of y = -x2 + 4x + 4 was obtained from the parent graph y = x2.

  1. The graph was shifted left 3 units and down 7 units.
  2. The graph was shifted left 7 units and down 7 units.
  3. The graph was shifted right 3 units and down 7 units.
  4. None of these are correct.

Back Button