cộng các phân số sau:
a)36/ -84 +100/450
b)-650/1430 +588/686
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a, \(\frac{-3}{7}\)+ \(\frac{2}{9}\)= \(\frac{-13}{63}\)
b, \(\frac{-5}{11}\)+ \(\frac{6}{7}\)= \(\frac{31}{77}\)
c, \(\frac{334}{335}\)+ \(\frac{-4}{335}\)= \(\frac{66}{67}\)
\(a)\frac{36}{-84}+\frac{100}{450}=\frac{-36}{84}+\frac{100}{450}\)
Rút gọn : \(\frac{-36}{84}=\frac{-36:12}{84:12}=\frac{-3}{7}\)
\(\frac{100}{450}=\frac{100:50}{450:50}=\frac{2}{9}\)
B1 : 7 = 7
9 = 32
\(\Rightarrow MSC=BCNN(7,9)=7\cdot3^2=63\)
B2 : Thừa số phụ :
63 : 7 = 9
63 : 9 = 7
B3 : Quy đồng :
\(\frac{36}{-84}=\frac{-36}{84}=\frac{-3}{7}=\frac{-3\cdot9}{7\cdot9}=\frac{-27}{63}\)
\(\frac{100}{450}=\frac{2}{9}=\frac{2\cdot7}{9\cdot7}=\frac{14}{63}\)
\(\Rightarrow\frac{-3}{7}+\frac{2}{9}=\frac{-27}{63}+\frac{14}{63}=\frac{-27+14}{63}=\frac{-13}{63}\)
b,c, Tự làm
65/91 + -33/55=4/35
36/-84 + 100/450=-13/63
-650/1430 + 588/686=31/77
20004/2010 + 8/-670=666/67
\(-\frac{650}{1430}+\frac{588}{686}=\frac{31}{77}\)
\(\frac{2004}{2010}+\frac{8}{-670}=\frac{66}{67}\)
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, \(\frac{2004}{2010}+\frac{8}{-670}=\frac{334}{335}+\frac{-4}{335}=\frac{66}{67}\)
\(\frac{36}{-84}+\frac{100}{450}\)
\(=\frac{3}{-7}+\frac{2}{9}\)
\(=-\frac{13}{63}\)
\(-\frac{650}{1430}+\frac{588}{686}\)
\(=-\frac{5}{11}+\frac{6}{7}\)
\(=\frac{31}{77}\)
\(a,\frac{36}{-84}+\frac{100}{450}\)
\(=-\frac{3}{7}+\frac{2}{9}\)
\(=\frac{-13}{63}\)
\(b,\frac{-650}{1430}+\frac{588}{686}\)
\(=-\frac{5}{11}+\frac{6}{7}\)
\(=\frac{31}{77}\)
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