In this Warm-up, students interpret points on a labeled graph. In the associated Algebra 1 lesson, students are introduced to function notation and understanding points in situations. This activity prepares students by asking them to think about the values in a situation given a visual graph. Students reason quantitatively when interpreting the values from the graph (MP2).

The purpose of the discussion is to talk about inputs and outputs of a function in context. Select students to share their responses. Here are some questions for discussion:

• "What is the temperature at 5:30 a.m.?" (It is not shown on the graph, so I do not know for sure. I would guess that it is around 12 degrees Celsius, though.)
• "On the news later, they say that the high temperature for the city on this day was 22 degrees Celsius. Is that reasonable? Explain your reasoning." (I believe it could happen. Sometime between 1 p.m. and 4 p.m. the temperature might have been up to 22 degrees Celsius, but not on the hour when the temperature was recorded in the graph.)
• "Would you believe the news if they say that the low temperature for the city on this day was 4 degrees? Explain your reasoning." (I would not believe it because the graph shows temperatures going only as low as 12 degrees Celsius, so it is unlikely to get that much colder and get back up to 12 degrees within the same hour.)

In this activity, students practice solving an equation after substituting in a value. In the associated Algebra 1 lesson, students will do a similar task using function notation. As students practice solving equations for a given value, they express regularity in repeated reasoning (MP8).

In this activity, students interpret a function in terms of a situation and examine some values that do not make sense in the situation. As students determine what is and is not a reasonable value, they model with mathematics (MP4). In the associated Algebra 1 lesson, students are introduced to function notation and interpret points in situations. Students are supported by this activity that provides them a chance to do all of the same work without the function notation so that they may focus on the new notation in the Algebra 1 lesson.