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Is It a Function? (Vertical Line Test) — Easy Worksheet 1
Grade 8 · Whoobee Name: ____________________ Date: __________
Does each graph show y as a function of x? Write Yes or No.
How to solve
Imagine sliding a vertical line across the graph. If a vertical line ever touches the graph in more than one place, one input has two outputs and the graph is not a function. If every vertical line touches it at most once, it is a function. A slanted or horizontal line passes the test; a vertical line fails it.
Example
Does the graph show y as a function of x? Write Yes or No.
Answer: No
Not quite. The answer is
💡 Each point has a different x-value (−5, −4, −3, 5), so no vertical line passes through two points. It is a function: Yes.
✓ Correct!
Not quite. The answer is
💡 Each point has a different x-value (−5, −4, −3, 5), so no vertical line passes through two points. It is a function: Yes.
💡 How to solve: Is It a Function? (Vertical Line Test)
Imagine sliding a vertical line across the graph. If a vertical line ever touches the graph in more than one place, one input has two outputs and the graph is not a function. If every vertical line touches it at most once, it is a function. A slanted or horizontal line passes the test; a vertical line fails it.
Try a similar one
Does the graph show y as a function of x? Write Yes or No.
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 Each point has a different x-value (−4, 0, 1, 4), so no vertical line passes through two points. It is a function: Yes.
✓ Correct!
Not quite. The answer is
💡 Each point has a different x-value (−4, 0, 1, 4), so no vertical line passes through two points. It is a function: Yes.
💡 How to solve: Is It a Function? (Vertical Line Test)
Imagine sliding a vertical line across the graph. If a vertical line ever touches the graph in more than one place, one input has two outputs and the graph is not a function. If every vertical line touches it at most once, it is a function. A slanted or horizontal line passes the test; a vertical line fails it.
Try a similar one
Does the graph show y as a function of x? Write Yes or No.
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 The points (−1, 1) and (−1, 3) lie on the same vertical line x = −1, so the input −1 has two outputs. It is not a function: No.
✓ Correct!
Not quite. The answer is
💡 The points (−1, 1) and (−1, 3) lie on the same vertical line x = −1, so the input −1 has two outputs. It is not a function: No.
💡 How to solve: Is It a Function? (Vertical Line Test)
Imagine sliding a vertical line across the graph. If a vertical line ever touches the graph in more than one place, one input has two outputs and the graph is not a function. If every vertical line touches it at most once, it is a function. A slanted or horizontal line passes the test; a vertical line fails it.
Try a similar one
Does the graph show y as a function of x? Write Yes or No.
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 Each point has a different x-value (−4, −3, −1, 2), so no vertical line passes through two points. It is a function: Yes.
✓ Correct!
Not quite. The answer is
💡 Each point has a different x-value (−4, −3, −1, 2), so no vertical line passes through two points. It is a function: Yes.
💡 How to solve: Is It a Function? (Vertical Line Test)
Imagine sliding a vertical line across the graph. If a vertical line ever touches the graph in more than one place, one input has two outputs and the graph is not a function. If every vertical line touches it at most once, it is a function. A slanted or horizontal line passes the test; a vertical line fails it.
Try a similar one
Does the graph show y as a function of x? Write Yes or No.
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 The points (1, 2) and (1, −5) lie on the same vertical line x = 1, so the input 1 has two outputs. It is not a function: No.
✓ Correct!
Not quite. The answer is
💡 The points (1, 2) and (1, −5) lie on the same vertical line x = 1, so the input 1 has two outputs. It is not a function: No.
💡 How to solve: Is It a Function? (Vertical Line Test)
Imagine sliding a vertical line across the graph. If a vertical line ever touches the graph in more than one place, one input has two outputs and the graph is not a function. If every vertical line touches it at most once, it is a function. A slanted or horizontal line passes the test; a vertical line fails it.
Try a similar one
Does the graph show y as a function of x? Write Yes or No.
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 Each point has a different x-value (−3, −1, 0, 1), so no vertical line passes through two points. It is a function: Yes.
✓ Correct!
Not quite. The answer is
💡 Each point has a different x-value (−3, −1, 0, 1), so no vertical line passes through two points. It is a function: Yes.
💡 How to solve: Is It a Function? (Vertical Line Test)
Imagine sliding a vertical line across the graph. If a vertical line ever touches the graph in more than one place, one input has two outputs and the graph is not a function. If every vertical line touches it at most once, it is a function. A slanted or horizontal line passes the test; a vertical line fails it.
Try a similar one
Does the graph show y as a function of x? Write Yes or No.
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 The points (3, 3) and (3, −5) lie on the same vertical line x = 3, so the input 3 has two outputs. It is not a function: No.
✓ Correct!
Not quite. The answer is
💡 The points (3, 3) and (3, −5) lie on the same vertical line x = 3, so the input 3 has two outputs. It is not a function: No.
💡 How to solve: Is It a Function? (Vertical Line Test)
Imagine sliding a vertical line across the graph. If a vertical line ever touches the graph in more than one place, one input has two outputs and the graph is not a function. If every vertical line touches it at most once, it is a function. A slanted or horizontal line passes the test; a vertical line fails it.
Try a similar one
Does the graph show y as a function of x? Write Yes or No.
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 The points (2, −2) and (2, 5) lie on the same vertical line x = 2, so the input 2 has two outputs. It is not a function: No.
✓ Correct!
Not quite. The answer is
💡 The points (2, −2) and (2, 5) lie on the same vertical line x = 2, so the input 2 has two outputs. It is not a function: No.
💡 How to solve: Is It a Function? (Vertical Line Test)
Imagine sliding a vertical line across the graph. If a vertical line ever touches the graph in more than one place, one input has two outputs and the graph is not a function. If every vertical line touches it at most once, it is a function. A slanted or horizontal line passes the test; a vertical line fails it.
Try a similar one
Does the graph show y as a function of x? Write Yes or No.
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
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Is It a Function? (Vertical Line Test) — Easy Worksheet 1
Does each graph show y as a function of x? Write Yes or No.