Question

A science class is tracking the progress of plant growth. The class starts the experiment with a plant five centimeters high. The plant grows two centimeters each day. The model for plant growth "y" is given by: y = 2x + 5. What is the meaning of the y-intercept in this equation?

Answer 1

The y intercept in this case means that the plant started off 5 centimeters high. If the plant grows two centimeters per day, then that means that the height is the y axis and days the x. Since in the very beginning, the plant was five centimeters high, that would be the y intercept, and then the plant would start growing from that height.

Answer 2

The second sentence above helps with this answer. The y-intercept is the initial height of the plant before any documentation of time and growth was collected. Since the plant was initially 5 cm high, we can use it as a starting point for the data. For example, using x=0 indicates 0 day and if we substitute it in you will see that we are left with a solution of 5. This will let those reading the data to understand that the plant was already at 5 cm when the experiment began.