\[\boxed{\text{511\ (511).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ 3^{2} + 4^{2} + 5^{2} = 6^{2}\]
\[9 + 16 + 25 = 6^{2}\]
\[50 \neq 36 \Longrightarrow равенство\ \]
\[неверное;\]
\[\textbf{б)}\ (1 + 2 + 3 + 4)^{2} = 10^{2} = 100\]
\[1^{3} + 2^{3} + 3^{3} + 4^{3} =\]
\[= 1 + 8 + 27 + 64 = 100\]
\[100 = 100\]
\[равенство\ \ (1 + 2 + 3 + 4)^{2} =\]
\[= 1^{3} + 2^{3} + 3^{3} + 4^{3} \Longrightarrow верное.\ \ \]