Решебник по математике 5 класс Ерина. Никольский рабочая тетрадь Часть 1, 2 Часть 1 | Страница 22

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\[\boxed{\mathbf{2.}}\]

\[a \cdot (b + c) = a \cdot b + a \cdot c\]

\[\boxed{\mathbf{3.}}\]

\[a \cdot (b - c) = a \cdot b - a \cdot c\]

\[a \cdot b + a \cdot c = a \cdot (b + c)\]

\[a \cdot b - a \cdot c = a \cdot (b - c)\]

\[\boxed{\mathbf{4.}}\]

\[\textbf{а)}\ a \cdot (b - c) = a \cdot b - a \cdot c\]

\[a \cdot (b + c) = a \cdot b + b \cdot c\]

\[\textbf{б)}\ a \cdot b + a \cdot c = a \cdot (b + c)\]

\[a \cdot b - a \cdot c = a \cdot (b - c)\]

\[\boxed{\mathbf{5.}}\]

\[\textbf{а)}\ 5 \cdot 81 = 5 \cdot (80 + 1) =\]

\[= 5 \cdot 80 + 5 \cdot 1 =\]

\[= 400 + 5 = 405\]

\[\textbf{б)}\ 7 \cdot 408 = 7 \cdot (400 + 8) =\]

\[= 7 \cdot 400 + 7 \cdot 8 =\]

\[= 2800 + 28 = 2828\]

\[\textbf{в)}\ 4 \cdot 397 = 4 \cdot (400 - 3) =\]

\[= 4 \cdot 400 - 4 \cdot 3 =\]

\[= 1600 - 12 = 1588\]

\[\textbf{г)}\ 4 \cdot 298 = 4 \cdot (300 - 2) =\]

\[= 4 \cdot 300 - 4 \cdot 2 =\]

\[= 1200 - 8 = 1192\]

\[\boxed{\mathbf{6.}}\]

\[\textbf{а)}\ 8 \cdot (a + 4) = 8a + 32\]

\[\textbf{б)}\ 11 \cdot (a + b + 7) =\]

\[= 11a + 11b + 77\ \]

\[\boxed{\mathbf{7.}}\]

\[\textbf{а)}\ (63 + 18 + 19) \cdot 100 =\]

\[= 100 \cdot 100 = 10\ 000\]

\[\textbf{б)}\ 1000\ :40 - 1000\ :100 =\]

\[= 25 - 10 = 15\]

\[\textbf{в)}\ (240 + 150)\ :2 - (240 - 150)\ :2 =\]

\[= 195 - 45 = 150\]

\[\textbf{г)}\ (1\ 000\ 000\ :100 - 1000)\ :1000 =\]

\[= 9000\ :1000 = 9\]