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.
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Answer:
y = 5x +4
Step-by-step explanation:
x has to equal 1
y = 5(1) +4 = 9
Answer:
-3x^4 - 13x^3 + 14x - 7
Step-by-step explanation:
(5x^4 – 9x^3 + 7x – 1) + (-8x^4 + 4x^2 – 3x + 2) - (-4x^3 + 5x - 1)(2x – 7)
simplify multiplied terms
(-4x^3 + 5x - 1)(2x – 7)
(-4x^3+10x-8)
group like terms together
(5x^4-8x^4) + (-9x^3-4x^3) + (7x-3x+10x) + (-1+2-8)
simplify grouped terms
-3x^4 - 13x^3 + 14x - 7
Answer:
x=1
Step-by-step explanation:
In order to solve this equation, we must add 7 to each side. This gives us x=1
