# Math Help - algebra help

1. ## algebra and trigonometry with analytic geometry problem

From a squqre piece of cardboard with width x inches, a square of width x-3 incues is removed from the center. Write the area of the remaining piece as a function of a. My answer is f(x)= 6x+9. But I'm not sure of my answer. thanks for the help.

2. Originally Posted by kwtolley
From a squqre piece of cardboard with width x inches, a square of width x-3 incues is removed from the center. Write the area of the remaining piece as a function of a. My answer is f(x)= 6x+9. But I'm not sure of my answer. thanks for the help.
Initial area is $x^2$, area of removed piece is $(x-3)^2$, so remaining area is:

$
f(x)=x^2-(x-3)^2=x^2-(x^2-6x+9)=6x-9
$

RonL