12. A veterinarian will prescribe an antibiotic to a dog based on its weight. The effective dosage of the antibiotic is given by d ≤ 1∕5w2, where d is dosage in milligrams and w is the dog's weight in pounds. Which of the following graphs displays the effective dosage of the antibiotic?

Graph C.  See explanations below.

Step-by-step explanation:

Looking for graph corresponding to   d <= (w^2)/5

Take the third graph, which has a solid line (to correspond to the inequality <=, or less than or equal to).

For a dog's weight of 10 lb, the corresponding dose is 20 mg = 10^2/5

for 20 lb, dose = 80 mg (=20^2/5)

...

For 40 lb, dose = 320 mg (=40^2/5).

So this is the correct graph.

The fourth (d) is similar. But the dotted line eliminates the equality in

d <= w^2/5

so not correct.

because linear equations are a lot simpler than quadratics equations, and linear equations formula is a lot easier to memorize. that's why i think they're harder.