ГДЗ по алгебре 7 класс Макарычев ФГОС Задание 1071

\[\boxed{\text{1071.}\text{\ }еуроки - ответы\ на\ пятёрку}\]

\[\textbf{а)}\ a(a - 4) - (a + 4)^{2} = a^{2} -\]

\[- 4a - \left( a^{2} + 8a + 16 \right) =\]

\[= a^{2} - 4a - a^{2} - 8a - 16 =\]

\[= - 12a - 16\]

\[если\ \ a = - 1\frac{1}{4} = - \frac{5}{4}:\]

\[- 12 \cdot \left( - \frac{5}{4} \right) - 16 = \frac{12 \cdot 5}{4} -\]

\[- 16 = 3 \cdot 5 - 16 = 15 -\]

\[- 16 = - 1.\]

\[\textbf{б)}\ (2a - 5)^{2} - 4 \cdot\]

\[\cdot (a - 1)(3 + a) = 4a^{2} - 20a +\]

\[+ 25 - 4 \cdot \left( 3a + a^{2} - 3 - a \right) =\]

\[= 4a^{2} - 20a + 25 - 12a -\]

\[- 4a^{2} + 12 + 4a = - 28a + 37\]

\[если\ a = \frac{1}{12}:\]

\[- \frac{28}{12} + 37 = - \frac{7}{3} + 37 =\]

\[= \frac{111 - 7}{3} = \frac{104}{3} = 34\frac{2}{3}.\]