Scientists are studying the temperature on a distant planet. Lety represent the temperature (in degrees Celsius). Letx represent the height above the surface (in kilometers). Suppose thatx andyare related by the equationY = 21 - 5x

Note that a change can be an increase or a decrease.

For an increase, use a positive number. For a decrease, use a negative number.

1 - What is the temperature change for each kilometer we go up from the surface? ____ C

2 - What is the temperature on the surface of the planet? _____ C