same as the one before a few way back.... so...check the picture below, then we use the pythagorean theorem
[tex]\bf (2s+9)^2=s^2+(2s+6)^2
\\\\\\
4s^2+36s+81=s^2+4s^2+24s+36\implies 36s+81=s^2+24s+36
\\\\\\
0=s^2-12s-45\implies 0=(s-15)(s+3)\implies
\begin{cases}
0=s-15\\
\boxed{15=s}\\
-----\\
0=s+3\\
-3=s
\end{cases}[/tex]
