\[a^2+b^2=c^2\]
It is
\[a=2mn, \: b=m^2-n^2, c=m^2+n^2, \: m \gt n\]
.We can show that these satisfy Pythagoras Theorem.
\[\begin{equation} \begin{aligned} a^2+b^2 &= (2mn)^2+(m^2-n^2)^2 \\ &= 4m^2n^2+m^4-2m^2n^2+n^4 \\ &= m^4+2m^2n^2+n^4 \\ &= (m^2+n^2)^2 \\ &= c^2 \end{aligned} \end{equation}\]