1. What do you notice? What do you think a function is?
This graph is a function.
This graph is a not function.
Not a function since the input -2 has two outputs 1 and -3.
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2. This graph is a function. This graph is a not function.
What do you notice? What do you think a function is?
This graph is a function.
This graph is a not function.
Not a function since the all inputs except x = 0 have two outputs.
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3. Is this graph a function? Defend your answer.
This is not a function since x = -1 has two outputs, 3 and -3.
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4. Is this graph a function? Defend your answer.
This is a function.
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5. Here is a way to test if a graph is a function.
The graph is a function. 
The Vertical Line Test. Pass a vertical line over the graph. If the vertical line touches the graph only once, then the graph is a function.
Now we show the vertical line test, but we still want students to develop their own understanding.
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6. Here is a way to test if a graph is a function.
The graph is not a function. 
The Vertical Line Test. Pass a vertical line over the graph. If the vertical line touches the graph more than once, then the graph is not a function. x x
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7. Is this graph of the k(x) pattern a function? Defend your answer.
This is a function.
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8. Is this graph a function? Defend your answer.
This is a function.
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9. Is this graph a function? Defend your answer.
This is not a function < x < has three outputs.
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10. Is this situation a function? Defend your answer.
The year a person was born and the first year they can get a driver’s license.
This is a function. Rule: birth year + 16 = driver’s license year.
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11. Is this situation a function? Defend your answer.
The forecasted high temperature of a day and the low temperature of the same day.
Click link to see forecasted our high and low temperatures.
This is not a function.
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12. ©Evergreen Public Schools 2010
Practice
Do this practice with your group.
Make copies each student.
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