Question

College Algebra http://prntscr.com/miy3fy

Answer 1

Find the derivative and then set it equal to 0

Answer 2

Because you've just gone


Derivative is \(-9.21x+71.36\)

\(-9.21x+71.36=0\)
\(-9.21x=-71.36\)
\(x=\frac{7136}{921}\approx x=7.74\approx 8\)

To find cost: Substitute the x value we got into the original eq
\(-4.605(\frac{7136}{921})^2+71.36(\frac{7136}{921})+96.91=373.362\)

Rounding to nearest tenth
\(373.3\color{green}{6}=\$373.40\)