\[\boxed{\text{830.}\text{\ }еуроки - ответы\ на\ пятёрку}\]
\[\textbf{а)}\ (a + 2b)^{2} = a² + 4ab + 4b²\]
\[*\ = a\]
\[\textbf{б)}\ (3x + a)^{2} = 9x² + 6ax + a²\]
\[*\ = a\]
\[\textbf{в)}\ (10 - 2m)^{2} = 100 -\]
\[- 40m + 4m²\]
\[*\ = 10\]
\[\textbf{г)}\ \left( 6a^{2} - 9c \right)^{2} = 36a^{4} -\]
\[- 108a^{2}c + 81c²\]
\[*\ = 6a^{2}\]
\[\textbf{д)}\ \left( 5y + 0,4x^{3} \right)^{2} = 25y² +\]
\[+ 4x³y + 0,16x^{6}\]
\[*\ = 0,4x^{3}\]
\[\textbf{е)}\ (3a + 2,5b)^{2} = 9a² +\]
\[+ 6,25b² + 15ab\ \]
\[*\ = 15\ ab\]