Question

The function below models the correlation between the number of hours a plant is kept in sunlight (x) and the height (y), in mm, to which it grows:
y = 4 + 2x
What does the y-intercept of this function represent?
The original height of the plant was 4 mm.
The original height of the plant was 2 mm.
The height of the plant increases by 2 mm for every hour of sunlight it receives.
The height of the plant increases by 4 mm for every hour of sunlight it receives.

Answer 1

Please read the question carefully for those looking at this from a exam.. I thought it said what does slope represent and I put original plant is 4mm ... ☹️

Answer 2

Remember that the y-intercept is obtained when the value of x is set to zero. This means that the y-intercept is the value of the height without sunlight yet. This also refers to the original height of the plant. This gives:

y = 4 + 2(0) = 4

So, the original height of the plant is 4 mm.

The formula also indicates that when sunlight is present, a height of 2mm is increased every hour of sunlight exposure.