so if say the width is "w", double that is 2*w, or 2w 1 unit less than that is 2w - 1, check the picture below
[tex]\bf A=length\cdot width\qquad
\begin{cases}
length = 2w-1\\
width = w\\
A=21
\end{cases}\implies 21=(2w-1)w
\\\\\\
21=2w^2-w\implies 0=2w^2-1-21
\\\\\\
0=(2w-7)(w+3)\implies
\begin{cases}
0=2w-7\implies &\boxed{\frac{7}{2}=w}\\\\
0=w+3\implies &-3=w
\end{cases}[/tex]
since it cannot be a negative value, so... is not -3
what are the dimensions? well, length = 2w - 1, and w = well is above :)
