Is it a function? Vertical line test, and reading values from graphs and tables

Answer Key - Grade 9 Math Worksheet

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

1. 1.

   Jun sketches a V-shaped sled run. Is the graph a function?

   • No: the horizontal line at y = 4 touches it twice
   • Yes: no vertical line touches it twice
   • No: it is not a straight line
2. 2.

   Kira traces a snail's curved trail, a sideways U. Is the graph a function?

   • Yes: every input has an output
   • Yes: it is a smooth curve with no breaks, so each input gets one output
   • No: the vertical line at x = 4 touches it at (4, 2) and (4, −2)
3. 3.

   Milo draws a U-shaped soup bowl. Is the graph a function?

   • No: it is not a straight line
   • Yes: no vertical line touches it twice
   • No: the horizontal line at y = 4 touches it twice
4. 4.

   Pia's puzzle uses the relation y = x² (x is the input). Test x = 3 and x = −3. Is it a function?

   • Yes: each input gives one output (3 and −3 both give 9)
   • No: the inputs 3 and −3 give the same output
   • No: any equation with a square in it fails the function test
5. 5.

   Ren's timer follows the relation |y| = x (x is the input). Test x = 5. Is it a function?

   • No: any equation with bars fails
   • Yes: the input 5 gives only y = 5
   • No: the input 5 gives y = 5 and y = −5
6. 6.

   Zee plots a machine's inputs and outputs. The graph shows f(x). What is f(−1)?

   -4
7. 7.

   Ari plots a kite's path. The graph shows f(x), the height in meters. What is f(−2)?

   3
8. 8.

   Bo plots a sneaker test. The graph shows f(x), a score. What is f(0)?

   -3
9. 9.

   Esme's bell rings louder over time. The graph shows f(x). For which x is f(x) = 5?

   2
10. 10.

    Kira's scarf grows longer. The graph shows f(x). For which x is f(x) = 8?

    4