Question

Вычеслите:
1) 25/28—2/21
2)41/54—35/72
3)20/21—3/14
4)40/143—39/110
5)43/140+41/150
6)73/80—37/100

Answer 1

$1)~dfrac{25}{28}-dfrac 2{21}=dfrac{25}{7cdot 4}^{(3}-dfrac {2}{7cdot 3}^{(4}=dfrac{25cdot 3-2cdot 4}{7cdot 4cdot 3}=dfrac{67}{84}\\2)~dfrac{41}{54}-dfrac {35}{72}=dfrac{41}{18cdot 3}^{(4}-dfrac {35}{18cdot 4}^{(3}=dfrac{41cdot 4-35cdot 3}{18cdot 3cdot 4}=dfrac{59}{216}\\3)~dfrac{20}{21}-dfrac {3}{14}=dfrac{20}{7cdot 3}^{(2}-dfrac {3}{7cdot 2}^{(3}=dfrac{20cdot 2-3cdot 3}{7cdot 3cdot 2}=dfrac{31}{42}$

$4)~dfrac{40}{143}-dfrac {39}{110}=dfrac{40}{11cdot 13}^{(10}-dfrac {39}{11cdot 10}^{(13}=dfrac{40cdot 10-39cdot 13}{11cdot 13cdot 10}=-dfrac{107}{1430}\\5)~dfrac{43}{140}+dfrac {41}{150}=dfrac{43}{14cdot 10}^{(15}+dfrac {41}{15cdot 10}^{(14}=dfrac{43cdot 15+41cdot 14}{14cdot 10cdot 15}=dfrac{1219}{2100}\\6)~dfrac{73}{80}-dfrac {37}{100}=dfrac{73}{20cdot 4}^{(5}-dfrac {37}{20cdot 5}^{(4}=dfrac{73cdot 5-37cdot 4}{20cdot 4cdot 5}=dfrac{217}{400}$