Is it a function? Inputs, outputs, domain and range

Answer Key - Grade 8 Math Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. Read this first

   Use the table

   input: x	output: y
   2.5	4
   -1	6
   0	4
   3	-2
   -1	7
   5	1

2. 1.

   Tala checks a table on the whiteboard before the bell. Is it a function, and why?

   • No: inputs 2.5 and 0 share the output 4
   • Yes: inputs -1, 0, 2.5, 3 and 5 each have an output
   • No: input -1 has two outputs, 6 and 7
3. 2.

   (3, 1/2), (-2, 4), (3, 2), (6, 4), (0, -3). Bo writes points for a grid design of a kite. Is it a function, and why?

   • Yes: inputs -2, 0, 3 and 6 each have an output
   • No: inputs -2 and 6 share the output 4
   • No: input 3 has two outputs, 1/2 and 2
4. 3.

   Jun plots six points in all four quadrants for a star map. Is it a function, and why?

   • No: the points are in all four quadrants of the grid
   • Yes: no two points are at the same height
   • No: (2, -4) and (2, 1) are on one up-and-down line
5. 4.

   Kira plots a zigzag path for a toy car race on a grid. Is it a function, and why?

   • No: (-3, -1) and (1, -1) are at the same height
   • Yes: inputs -5, -3, 0, 1, 3 and 5 each have one point
   • No: the points are not on one straight line
6. 5.

   Luz plots five points from a mystery rule, then squints at them. Is it a function, and why?

   • No: the points do not go through (0, 0), so it fails
   • No: (-4, 1) and (0, 1) are at the same height
   • No: (3, -3) and (3, 2) are on one up-and-down line

7. Use the table

   input: x	output: y
   1/2	3
   2	-1
   4	3
   -3	1/4
   6	5

8. 6.

   Tala fills in a rule table with fractions. What is the range (all the outputs)? List each value once.

   -1, 1/4, 3, 5
9. 7.

   (2, 7), (-6, 0), (2, 7), (1/2, 4), (9, -5). Zee lists points, and one pair got written twice. What is the domain (all the inputs)? List each value once.

   -6, 1/2, 2, 9
10. 8.

    Ari plots points for a robot's path, and the robot got confused. This graph is not a function. Which input has two different outputs?

    -2
11. 9.

    Kira's pairs make a function: (-2, 5), (0, 1), (3, 5), (7, -4). Which new pair can join and keep it a function?

    • (0, 3)
    • (7, 5)
    • (4, 1)
12. 10.

    Luz's pairs make a function: (-5, -2), (-1, 3), (2, 0), (6, 3). Which new pair can join and keep it a function?

    • (-1, -2)
    • (1, -2)
    • (2, 6)