# Thread: Help Finding Perimeter of Rectangle

1. ## Help Finding Perimeter of Rectangle

Hello,
I am studying to take a math placement exam in two days. There's this one geometry problem that I cannot figure out how to solve. I watched a video of someone solving it but I don't understand what they're doing after a certain point. Here's the problem:

I don't know if it's just me but I think his approach to solve it is way too complicated. Does anybody know another way to solve this problem other than what he's doing? I know how to factor well but even with that what he's doing is still confusing me. I'll leave screenshots of what the guy in the video did but I am drawing a blank in this one.
(I understand what he did up to this picture, after that I don't really know why he's doing all that)

Here's the rest of his work:

2. ## Re: Help Finding Perimeter of Rectangle

$l \times w = 96$

$w = l - 4$

$l(l-4)=96$

$l^2 - 4l - 96 = 0$

$l^2 - 4l + 4-4-96 = 0$

$(l-2)^2 -100 = 0$

$(l-2)^2 = 100$

$l - 2 = 10$ (we can ignore the negative solution)

$l = 12$

$w = l-4 = 8$

$P= 2(l+w) = 2(12+8) = 40$