9514 1404 393
Answer:
C. (1, 1), (2, 0), and (-1, -3)
Step-by-step explanation:
I find it works well to solve this graphically. That seems easier than solving 3 sets of simultaneous equations.
The points of intersection of the three lines are ...
(1, 1), (2, 0), and (-1, -3) . . . . matches C
X + y = 40
y = 9x
x + 9x = 40 (substitute 9x for y in 1st equation)
10 x = 40
x = 4
4 + y = 40 (substitute 4 for x in 1st equation)
y = 36
You have to test dp/dt between these intervals
(-inf,2)
(2,10)
(10,inf)
if dp/dt is positive then the population is increasing with respect to time in that interval