-5/7+7/-5+4/7+7/4= 2/-5+-3/7+-7/10+3/-8= x-2/35=-3/25 11/12-(x+2/5)=2/3 bài 2 so sánh 0,25 và 13/12 2/3 và 6/7

Đáp án:

 $-\dfrac{5}{7} +\dfrac{7}{-5} +\dfrac{4}{7}+\dfrac{7}{4} = \dfrac{-100}{140} + \dfrac{-196}{140} + \dfrac{80}{140} +\dfrac{245}{140} = \dfrac{29}{140}$

$\dfrac{2}{-5} +\dfrac{-3}{7} +\dfrac{-7}{10} +\dfrac{3}{-8} = \dfrac{-224}{560} + \dfrac{-240}{560} +\dfrac{-392}{260} + \dfrac{-210}{560} = -\dfrac{1066}{560} = -\dfrac{533}{280}$

$x-\dfrac{2}{35} = -\dfrac{3}{25}$

$ ⇔ x = -\dfrac{3}{25}+\dfrac{2}{35}$

$⇔ x = -\dfrac{11}{175}$

Vậy $x=-\dfrac{11}{175}$

$\dfrac{11}{12} -(x+\dfrac{2}{5}) =\dfrac{2}{3}$

$⇔ x +\dfrac{2}{5} =\dfrac{11}{12} -\dfrac{2}{3}$

$⇔ x +\dfrac{2}{5}  =\dfrac{1}{4}$

$⇔ x = \dfrac{1}{4} - \dfrac{2}{5}$

$⇔ x = -\dfrac{3}{20}$

Vậy $x=-\dfrac{3}{20}$

Bài 2 :

$0,25 $ và $\dfrac{13}{12}$

$\dfrac{1}{4}$ và $\dfrac{13}{12}$

$⇒\dfrac{1}{4} = \dfrac{3}{12}$

Vì $\dfrac{3}{12} < \dfrac{13}{12}$

Nên $\dfrac{1}{4} < \dfrac{3}{12}$

Hay $0,25 < \dfrac{13}{12}$

$\dfrac{2}{3}$ và $\dfrac{6}{7}$

$⇒\dfrac{2}{3} = \dfrac{14}{21}$

$⇒\dfrac{6}{7} =\dfrac{18}{21}$

Vì $\dfrac{14}{21} < \dfrac{18}{21}$

Nên $\dfrac{2}{3} < \dfrac{13}{12}$