Question

1) 3/5+4 1/5×(4/21-3/14)-3/5=
2) |7x-5|+4×|5-7x|=​

Answer 1

Ответ:

$\displaystyle \bold 1) \; -\dfrac{1}{10}$

2) 5·|5-7·x|

Пошаговое объяснение:

$\displaystyle \bold 1) \; \dfrac{3}{5} +4\dfrac{1}{5} \cdot (\dfrac{4}{21}-\dfrac{3}{14})-\dfrac{3}{5}=-\dfrac{1}{10}.$

Изменим расположения дробей и получим:

$\displaystyle \bold \; \dfrac{3}{5}-\dfrac{3}{5} +4\dfrac{1}{5} \cdot (\dfrac{4}{21}-\dfrac{3}{14})=4\dfrac{1}{5} \cdot (\dfrac{4}{21}-\dfrac{3}{14})=-\dfrac{1}{10}.$

$\displaystyle \bold 1. \; \dfrac{4}{21}-\dfrac{3}{14}=\dfrac{4 \cdot 2}{21 \cdot 2}-\dfrac{3 \cdot 3}{14 \cdot 3}=\dfrac{8}{42}-\dfrac{9}{42}=\dfrac{8-9}{42}=-\dfrac{1}{42};$

$\displaystyle \bold 2. \; 4\dfrac{1}{5} \cdot (-\dfrac{1}{42})=-\dfrac{21}{5} \cdot \dfrac{1}{21 \cdot 2}=-\dfrac{21 \cdot 1}{5 \cdot 21 \cdot 2}=-\dfrac{1}{5 \cdot 2}=-\dfrac{1}{10}.$

2) |7·x-5|+4·|5-7·x| = |7·x-5|+4·|-(7·x-5)| = |7·x-5|+4·|7·x-5| = 5·|7·x-5|.