Lesson 23

Comparing Functions

  • Let’s evaluate and compare functions.

23.1: Math Talk: Evaluating Functions

Mentally evaluate each of the functions when x = 3.

f(x) = x^2 - 4x + 1

g(x) = 6x - 2x^2

h(x) = (x-4)(x-3)

j(x) = 2(x-1)(x+2)

23.2: Comparing Functions

The notation f(2) means the output of function f when x is 2. For each function, determine whether f(2) > f(3), f(2) < f(3), or f(2) = f(3).

  1. f(x) = x^2 + 2x+ 3
  2. f(x) = (x-2)(x-3)
  3. f(x) = \text{-}x^2 + 5
  4. Graph on coordinate plane.
  5. Graph of line on coordinate plane.
  6. Graph on coordinate plane. Horizontal axis by twos from negative 4 to 8. Vertical axis by twos from negative 4 to 8. Graph goes through point 0 comma 8.
  7. Graph of wiggly line on coordinate plane. Horizontal axis by twos from negative 4 to 8. Vertical axis by twos from negative 4 to 8. Graph goes through origin.

23.3: Finding the Vertex

Write each function in vertex form, then find the coordinates of the vertex.

  1. y = x^2 - 4x + 7
  2. y = (x-1)(x+3)
  3. y = (x-2)(x+2)
  4. y = x^2 - 2x + 1
  5. y = \text{-}x^2 -2x-6
  6. y = 2x^2 - 12x + 22
  7. Graph on coordinate plane. Horizontal axis by twos from negative 8 to 8. Vertical axis by twos from negative 4 to 8. Graph goes through point 0 comma 7.

Summary