Confusing...please help!

[Maryanne]

I was understanding operations with polynomials until I came across this question any help would be greatly appreciated.

Question:

A packaging company makes boxes with no tops. One style of box is made from cardboard 20 cm long and 10 cm wide. Equal squares are cut from the corners and the sides are folded up.

Let X represent the side length of each square cut out. Write a polynomial to represent the surface area of the box.

The answer is A=-4x²+200 I understand how they got the 200 but not the negative four......

 

[Denis]

A packaging company makes boxes with no tops. One style of box is made from cardboard 20 cm long and 10 cm wide. Equal squares are cut from the corners and the sides are folded up.
Let X represent the side length of each square cut out. Write a polynomial to represent the surface area of the box.
The answer is A=-4x²+200 I understand how they got the 200 but not the negative four......

You must be trying too hard Maryanne; it's really simple:

The cut off squares each have area x^2, since the sides = x;
so that's a total of 4x^2.
The area BEFORE cutoffs = 20 * 10 = 200

So after cutoffs: 200 - 4x^2

Kick yourself :wink:

 

[Maryanne]

yea I do tend to overlook simple questions, thanks for you help Denis!

 

[Denis]

yea I do tend to overlook simple questions, thanks for you help Denis!

Well, you ain't alone.
The other day, I was looking at this "what's next" sequence:
S M T W T F ?
I was trying complicated number stuff, like S=19...
My 8 years old granddaughter Brittany has one look and says:
S for Saturday!
"hmmm...I knew that", I said, "was just trying something else!"