Richard C. answered 07/20/22
Confidence-building Geometry tutor with 18 years experience
Of course you could solve this with calculus by finding P'(x) and setting that to zero.
But if you realize that this is a parabola opening down, then the maximum can be found by
x = -b/2a = -110/(2(-1)) = 55.
Find the profit by P(55) = 2025.