Question

490. Вычислите 1) (1/4 - 2/3) * (4/5 - 2/15) * (-3/5) 2) (1/6 - 5/9) * (1/2 - 3/7) * 7 1/5​

Answer 1

Ответ:

Пошаговое объяснение:

№1

$\left(\dfrac{1}{4} -\dfrac{2}{3} \right)\cdot\left( \dfrac{4}{5} -\dfrac{2}{15}\right)\cdot \left(- \dfrac{3}{5} \right)=\dfrac{1}{6}$

$1) \dfrac{1}{4} -\dfrac{2}{3}=\dfrac{1}{4}^{\backslash3} -\dfrac{2}{3}^{\backslash4}= \dfrac{3}{12} -\dfrac{8}{12} =- \dfrac{5}{12} ;\\\\2) \dfrac{4}{5} -\dfrac{2}{15}= \dfrac{4}{5}^{\backslash3} -\dfrac{2}{15}^{\backslash1}=\dfrac{12-2}{15} =\dfrac{10}{15} =\dfrac{10:5}{15:5} =\dfrac{2}{3} ;\\\\3) -\dfrac{5}{12} \cdot \dfrac{2}{3} \cdot \left(- \dfrac{3}{5} \right)= \dfrac{5\cdot 2\cdot3}{6\cdot2\cdot 3\cdot5} =\dfrac{1}{6}$

№ 2

$\left(\dfrac{1}{6} -\dfrac{5}{9}\right) \cdot\left(\dfrac{1}{3} -\dfrac{3}{7}\right) \cdot 7\dfrac{1}{5}=\dfrac{4}{15}$

$1)\dfrac{1}{6} -\dfrac{5}{9} =\dfrac{1}{6}^{\backslash3} -\dfrac{5}{9}^{\backslash2}=\dfrac{3}{18}-\dfrac{10}{18} = -\dfrac{7}{18} ; \\\\2) \dfrac{1}{3} -\dfrac{3}{7}=\dfrac{1}{3}^{\backslash7} -\dfrac{3}{7}^{\backslash3}= \dfrac{7}{21} -\dfrac{9}{21}=-\dfrac{2}{21};\\\\3) -\dfrac{7}{18}\cdot \left(- \dfrac{2}{21}\right )\cdot 7\dfrac{1}{5} = \dfrac{7}{18} \cdot \dfrac{2}{21} \cdot \dfrac{36}{5} =\dfrac{7\cdot2\cdot 2\cdot18}{18\cdot3\cdot7\cdot5} =\dfrac{4}{15}$