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Tính :
a) 65 / 91 + -33 / 55
\(=\frac{5}{7}-\frac{3}{5}=\frac{4}{35}\)
b) 36 / -84 + 100 // 450
\(=\frac{-3}{7}+\frac{2}{9}=-\frac{13}{63}\)
c) -650 / 1430 + 588 / 686
\(=\frac{5}{11}+\frac{6}{7}=\frac{101}{77}\)
d) 2004 / 2010 + 8 / -670
=\(=\frac{334}{335}-\frac{4}{335}=\frac{66}{67}\)
a, \(\frac{65}{91}+\frac{-33}{55}=\frac{5}{7}+\frac{-3}{5}=\frac{4}{35}\)
b, \(\frac{36}{-84}+\frac{100}{450}=\frac{-3}{7}+\frac{2}{9}=-\frac{13}{63}\)
c, \(\frac{-650}{1430}+\frac{588}{686}=\frac{-5}{11}+\frac{6}{7}=\frac{31}{77}\)
d, \(\frac{2004}{2010}+\frac{8}{-670}=\frac{334}{335}+\frac{-4}{335}=\frac{66}{67}\)
a, Ta có: 10 = 2.5; 12 = 2 2 .3
BCNN(10,12) = 2 2 .3.5 = 60
b, Ta có: 24 = 2 3 .3; 56 = 2 3 .7
BCNN(24;56) = 2 3 .3.7 = 168
c, Ta có: 84 = 2 2 .3.7; 108 = 2 2 . 3 3
BCNN(84;108) = 2 2 . 3 3 .7
d, Ta có: 33 = 3.11; 44 = 4.11; 55 = 5.11
BCNN(33;44;55) = 3.4.5.11 = 660
e, Ta có: 8 = 2 3 ; 18 = 2. 3 2 ; 30 = 2.3.5
BCNN(8,18,30) = 2 3 . 3 2 . 5 = 360
f, Ta có: 40 = 2 3 . 5 ; 28 = 2 2 .7; 140 = 2 2 .5.7
BCNN(40;28;140) = 2 3 . 5 . 7 = 280
a; \(\dfrac{9}{27}\) + \(\dfrac{7}{-49}\)
= \(\dfrac{1}{3}\) - \(\dfrac{1}{7}\)
= \(\dfrac{7}{21}\) - \(\dfrac{3}{21}\)
= \(\dfrac{4}{21}\)
b; - \(\dfrac{12}{10}\) + \(\dfrac{-25}{30}\)
= - \(\dfrac{6}{5}\) - \(\dfrac{5}{6}\)
= -\(\dfrac{36}{30}\) - \(\dfrac{25}{30}\)
= \(\dfrac{-61}{30}\)
c; \(\dfrac{-20}{35}\) + \(\dfrac{-16}{-24}\)
= - \(\dfrac{4}{7}\) + \(\dfrac{2}{3}\)
= - \(\dfrac{12}{21}\) + \(\dfrac{14}{21}\)
= \(\dfrac{2}{21}\)
d; - \(\dfrac{21}{77}\) + \(\dfrac{10}{-35}\)
= - \(\dfrac{3}{11}\) - \(\dfrac{2}{7}\)
= - \(\dfrac{21}{77}\) - \(\dfrac{22}{77}\)
= - \(\dfrac{43}{77}\)
a.={75+(-75)}+{15+(-32)}+-55
=0+-17+-55
=0+{(-17)+(-55)
=0+-75
=-75
b. =(35+35)+(65-65)+(24-24)
=70+0+0
=70
không biết đúng hay sai mong mấy bạn thông cảm vì mình cũng không chắc chắn !