The total profit (in dollars) from the sale of x answering machines is
P(x)=20x−0.7x2−280.
a. Find the exact profit from the sale of the 26th machine.
Exact Profit on 26th machine =
b. Use the marginal profit to approximate the profit from the sale of the 26th machine.
Approx. profit on 26th machine =
(a) the profit from the 26th sale is p(26)-p(25) = -15.7
oddly enough, P(x) is negative everywhere. Is there a typo? That -280 term indicates a pretty big fixed cost.
(b) dp/dx = 20-0.14x
use that to find the marginal profit