Ryan conducted a 6 day study on the effect of plant food on his plants. he found the amount of plant food remaining decreased an equal amount each day and he used all 72 milliliters by the end of his study. write a function rule of the relationship between amount of plant food remaining, f(x) and the number of days that have passed.

Step-by-step explanation:

Givens

According to the problem, if Ryan used 72 milliliters in 6 days, that means he used per day:

If we call days, and the amount of plant food remaining, the expression that models this situation is

Where the constant ratio of change is 12, and it's negative, because the plant food is decreasing.

Notice that we use a linear function to model the situation, because the problem speficies that the plant food decreases an equal amount each day, which refers to the constant ratio of change, which is a linear ratio.