Answer:
The two values of production level are:
x = 20
or
x = 140
Step-by-step explanation:
Let's write the Profit equation by subtracting the cost function from the revenue one:
[tex]Profit(x)=100\,x-0.5\,x^2-(20\,x+700)\\Profit(x)=-0.5\,x^2+80\,x-700[/tex]
Now, we set to find the production level "x" to give us a profit of $ 700:
[tex]Profit(x)=-0.5\,x^2+80\,x-700\\700=-0.5\,x^2+80x-700\\0.5\,x^2-80\,x+1400=0[/tex]
So we solve this quadratic equation using the quadratic formula:
[tex]x=\frac{80+/-\sqrt{80^2-4(0.5)(7700)}}{2\,*\,0.5} \\x=80+/-\sqrt{3600} \\x=80\,+/-\,60[/tex]
which gives two posible solutions: x = 20, or x = 140