Prove that $\displaystyle a^2+b^2=c^2$ using:

$\displaystyle a=m^2-n^2$

$\displaystyle b=2mn$

$\displaystyle c=m^2+n^2$

So far I have got:

(m*m)(m*m)-(n*n)(n*n)+4(m*m)(n*n)=(m*m)(m*m)-(n*n)(n*n)

What can I do with 4(m*m)(n*n)?

Can I do (m*m)+(m*m)+(m*m)+(m*m)*(n*n)+(n*n)+(n*n)+(n*n)

???

~Cyf