Question

The equation C(l) = l3 – l2 + l + 2.5 models the cost to mail a package as a function of its length. To the nearest quarter inch, approximately what is the length of a package that costs $11.00 to mail? Enter your answer as a decimal.

inches

Answer 1

Solve l^3 − l^2 + l + 2.5 = 11 → l^3 − l^2 + l − 8.5 = 0. The real root is about l ≈ 2.243 (by numeric approximation). To the nearest quarter inch this is 2.25 inches.