Answer
$9x^{2}-24x+16$.
Work Step by Step
The area of a square with side a:
$A=a^{2}$
...substitute $(3x-4)$ for $a$.
$A=(3x-4^{2})$
...square the binomial.
$A=(3x^{2})-2(3x)(4)+4^{2}$
...simplify.
$A=9x^{2}-24x+16$
The area of the base is $9x^{2}-24x+16$.
