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a) 19/35+15/19+16/35+23/19+4/15+11/15 = (19/35+16/35)+(15/19+23/19)+(4/15+11/15) = 1+2+1 = 4 b)4/17-7/15+13/17-8/15+5/8-7/16 = (4/17+13/17)-(7/15-8/15)+(5/8-7/16) = 1-1+3/16 =3/16
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\(\dfrac{19}{28}+\dfrac{23}{47}-\dfrac{15}{8}+\dfrac{9}{28}+\dfrac{24}{47}\)
\(=\left(\dfrac{19}{28}+\dfrac{9}{28}\right)+\left(\dfrac{23}{47}+\dfrac{24}{47}\right)-\dfrac{15}{8}\)
\(=\dfrac{28}{28}+\dfrac{47}{47}-\dfrac{15}{8}\)
\(=1+1-\dfrac{15}{8}\)
\(=\dfrac{1}{8}\)
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\(\dfrac{30}{11}+\dfrac{12}{35}-\dfrac{19}{11}-\dfrac{2}{35}-\dfrac{2}{7}\)
\(=\left(\dfrac{30}{11}-\dfrac{19}{11}\right)+\left(\dfrac{12}{35}-\dfrac{2}{35}\right)-\dfrac{2}{7}\)
\(=\dfrac{11}{11}+\dfrac{10}{35}-\dfrac{2}{7}\)
\(=1+\dfrac{2}{7}-\dfrac{2}{7}\)
\(=1\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Suy nghĩ: rút gọn các phân số chưa tối giản rồi so sánh:
Ta có:
![](https://rs.olm.vn/images/avt/0.png?1311)
đầu bài: 1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20
= (1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+20
= 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 +20
= 20.10
= 200
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20=\(\frac{\left(1+20\right)20}{2}\)=210
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(\frac{9}{15}+\frac{8}{11}\right)+\frac{6}{15}=\left(\frac{9}{15}+\frac{6}{15}\right)+\frac{8}{11}\)
\(=1+\frac{8}{11}=\frac{19}{11}\)
\(\left(\frac{26}{17}+\frac{15}{34}\right)+\left(\frac{8}{17}+\frac{19}{34}\right)=\left(\frac{26}{17}+\frac{8}{17}\right)+\left(\frac{15}{34}+\frac{19}{34}\right)\)
\(=2+1=3\)
\(\left(\frac{9}{15}+\frac{8}{11}\right)+\frac{6}{15}\)
\(=\left(\frac{9}{15}+\frac{6}{15}\right)+\frac{8}{11}\)
\(=1+\frac{8}{11}\)
\(=\frac{19}{11}\)
\(\left(\frac{26}{17}+\frac{15}{34}\right)+\left(\frac{8}{17}+\frac{19}{34}\right)\)
\(=\frac{26}{17}+\frac{15}{34}+\frac{8}{17}+\frac{19}{34}\)
\(=\left(\frac{26}{17}+\frac{8}{17}\right)+\left(\frac{15}{34}+\frac{19}{34}\right)\)
\(=2+1\)
\(=3\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{19}{35}+\frac{15}{19}+\frac{16}{35}+\frac{23}{19}+\frac{4}{15}+\frac{11}{15}\)
\(=\left(\frac{19}{35}+\frac{16}{35}\right)+\left(\frac{15}{19}+\frac{23}{19}\right)+\left(\frac{4}{15}+\frac{11}{15}\right)\)
\(=\frac{35}{35}+\frac{38}{19}+\frac{15}{15}\)
\(=1+2+1\)
\(=4\)
\(\frac{19}{35}+\frac{15}{19}+\frac{16}{35}+\frac{23}{19}+\frac{4}{15}+\frac{11}{15}\)
\(=\left(\frac{19}{35}+\frac{16}{35}\right)+\left(\frac{15}{19}+\frac{23}{19}\right)+\left(\frac{4}{15}+\frac{11}{15}\right)\)
\(=1+2+1\)
\(=4\)
Học tốt
![](https://rs.olm.vn/images/avt/0.png?1311)
= ( 19/35 + 16/35 ) + ( 15/19 + 23/19 ) + ( 4/15 + 11/15 )
= 1 + 2 + 1
= 4
Cái chỗ mà 2032 là dấu cách nhé cá bạn
có nghĩa là 11/15 +(8/9+19/15)