CPM Homework Help : CALC Problem 8-106

Multiple Choice: If $y = 3x − 12$ , then the minimum product for $xy$ is:

$−9$

$−12$

$−18$

Hint:

Before using Calculus, write an equation with only one variable. Let $f(x) = xy$ . Then use $y = 3x − 12$ to solve write $f(x)$ in terms of $x$ only.

More Help:

Optimize. Remember that you are looking for the minimum product, not the minimum value of $x$ .