Whenever you face the problem that deals with maxima or minima you should keep in mind that minima/maxima of a function is always a point where it's derivative is equal to zero.
To solve your problem we first need to find an equation of net benefits. Net benefits are expressed as a difference between total benefits and total cost. We can denote this function with B(y).
B(y)=b-c
B(y)=100y-18y²
Now that we have a net benefits function we need find it's derivate with respect to y.

Now we must find at which point this function is equal to zero.
0=100-36y
36y=100
y=2.8
Now that we know at which point our function reaches maxima we just plug that number back into our equation for net benefits and we get our answer.
B(2.8)=100(2.8)-18(2.8)²=138.88≈139.
One thing that always helps is to have your function graphed. It will give you a good insight into how your function behaves and allow you to identify minima/maxima points.
Answer:
Answer 10 min
Step-by-step explanation:
Because if it crawls 40 cm per minute but it goes back 10 cm because of wind then you have to do 40-10 = 30 then you do 300 divided by 30 to get the time.
Hope this helped!!!
Answer:
Yes, (-3, -9) is a solution.
Step-by-step explanation:
y = 3x (-3,-9)
-9 = 3(-3)
-9 = -9

Step-by-step explanation:
1) Collect like terms.

2) Simplify.

So, therefor, the answer is -17y - 16z + 4.