Answer:
[tex]21\: \mathrm{feet\: by}\: 11 \: \mathrm{feet}[/tex]
Step-by-step explanation:
(Assuming the den is a rectangle)
Let [tex]x[/tex] be the length of the den. Because the length is 10 feet longer than the width, the width of the den can be represented as [tex]x-10[/tex].
The area of a rectangle is given as [tex]l\cdot w[/tex], therefore we can form the following equation:
[tex]x(x-10)=231[/tex]
Expanding this, we have:
[tex]x^2-10x=231, \\\\x^2-10x-231=0[/tex]
This factors into [tex](x-21)(x+11)=0[/tex], therefore [tex]x=21, \: -11[/tex].
Because -11 is extraneous, the length of the den is [tex]21[/tex] feet and the width is [tex]21-10=11[/tex]. Thus, the dimensions of the den are [tex]\fbox{$21\: \mathrm{feet\: by}\: 11 \: \mathrm{feet}$}[/tex].
