Kathy G. answered 11/20/20
Experienced Math tutor with 40 years experience
This is a parabola opening down so the vertex will give us the maximum value.
Use x = -b/2a. to get x= -200/(2x-2) = -200/-4. = 50
So 50 phones should be made. To find the profit substitute x=50 into the original equation.
This gives y =. -2 (50)^2 + 200(50). +. 25000. = 30000