standard_description: (+)Derive the equations of ellipses and hyperbolas given the foci, using the fact that the sum or difference of distances from the foci is constant.
problem_activity: Activity
The purpose of this activity is to give students practice writing and graphing equations from situations. In the next activity and in the supported Algebra 1 lesson, students will write and graph inequalities  Students then assess the meaning of points off of the line in the situation provided and interpret whether those points might be valid in the situation.
Student Facing
Write an equation that helps to answer the question about the situation. Then draw a graph that represents the equation.
Jada goes to an orchard to pick plums and apricots to make jam. She picks 20 pounds of fruit altogether. If she picks
\(a\)
pounds of apricots, how many pounds of plums does she pick?
[IMG]
Consider the point
\((5,16)\)
. Is it possible for the weight of the fruit to be represented by that point in this situation? Explain your reasoning.
In a video game, a character can run at a top speed of 30 miles per hour, but each additional pound that the character carries lowers the maximum running speed by 1 mile per hour. What is the maximum running speed of the character when they are carrying
\(w\)
pounds?
[IMG]
Consider the point
\((10,15)\)
. Is it possible for a character in this game to be represented by that point in this situation? Explain your reasoning.
Student Response
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Activity Synthesis
The purpose of the discussion is to examine points on and off the lines and determine what they might mean in the situations.
Ask students:
"What are the coordinates for a point on the line that represents the scooter situation? What do the coordinates mean in that situation?" (The point
\((1,22)\)
is on the line. This means that renting the scooter for 2 hours should cost
$
22.)
"What are the coordinates for a point above the line that represents the scooter situation? What do the coordinates mean in that situation? Is it realistic?" (The point
\((2,30)\)
is above the line. This means paying
$
30 for 2 hours with a scooter. It only makes sense if the person is overpaying for some reason like if they broke part of the scooter and have to pay extra.)
"The point
\((5,30)\)
is above the line that represents the maximum run speed for the videogame character. Describe a situation where this might be possible." (If the character has an item that ignores the carry weight or something that boosts their run speed, then maybe this is possible.)


aligns: no