\[2a(3a + 4b) - 5b(a + b) - 5a^{2} -\]
\[- 3ab + 6b^{2} = \ 6a^{2} + 8ab - 5ab - 5b^{2} -\]
\[- 5a^{2} - 3ab + 6b^{2} = a^{2} + b^{2}\ \]
\[(вторая\ степень)\]