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7/12-2/7+1/12=7/12+1/12-2/7=8/12-2/7=2/3+2/7=14/21+6/21=20/21
12/17-5/17-4/17=3/17

1.
a) 889972 + 96306 = 986278
b) 726,83 - 349,67 = 377,16
c) \(\frac{7}{8}+\frac{3}{4}=\frac{13}{8}\)
d)\(2-\frac{5}{6}=\frac{7}{6}\)

a: \(\frac79-\frac{4}{15}+\frac61\)
\(=\frac{35}{45}-\frac{12}{45}+6\)
\(=6+\frac{23}{45}=\frac{270}{45}+\frac{23}{45}=\frac{293}{45}\)
b: \(\frac{44}{21}-\left(\frac34+\frac{2}{21}\right)\)
\(=\frac{44}{21}-\frac{2}{21}-\frac34\)
\(=2-\frac34=\frac54\)
c: \(\frac{17}{12}+\frac{13}{7}-\frac67+\frac{7}{12}\)
\(=\frac{17}{12}+\frac{7}{12}+\left(\frac{13}{7}-\frac67\right)\)
=2+1
=3

2/5 + 3/4 = 23/40
7/12 - 2/7 + 1/12 = 25/84 + 1/12 = 8/21
12/17 - 5/17 - 4/17 = 3/17
OK
\(\frac{2}{5}+\frac{3}{4}=\frac{8}{20}+\frac{15}{20}=\frac{23}{20}\)
\(\frac{7}{12}-\frac{2}{7}+\frac{1}{12}=\left(\frac{7}{12}+\frac{1}{12}\right)-\frac{2}{7}=\frac{2}{3}-\frac{2}{7}=\frac{14}{21}-\frac{6}{21}=\frac{8}{21}\)
\(\frac{12}{17}-\frac{5}{17}-\frac{4}{17}=\frac{12-5-4}{17}=\frac{3}{17}\)

a) \(\dfrac{2}{3}+\dfrac{3}{5}=\dfrac{10}{15}+\dfrac{9}{15}=\dfrac{19}{15}\)
a) \(\dfrac{7}{12}-\dfrac{2}{7}+\dfrac{1}{12}=\dfrac{2}{3}-\dfrac{2}{7}=\dfrac{14}{21}-\dfrac{6}{21}=\dfrac{8}{21}\)

a) 2/5+3/4=23/20
7/12-2/7+1/12=8//21
12/17-5/17-4/17=3/17
b) 675,39+342,14=1017,53
563,87+403,13-328,35=638,65
a) 2/5+3/4
=8/20+15/20
=21/20
7/12-2/7+1/12
=7/12+1/12-2/7
=1/4-2/7
=7/28-8/28
=-1/28
12/17-5/17-4/17
=12/17-9/17
=3/17
b) 675,39+342,14
= 1017,53
563,87+403,13-328,35
= 967-328,35
= 638,65

2 - 5/6= 7/6
7/8+3/4=`13/8
2/5+3/4=23/20
7/12 - 2/7 + 1/12=8/21
12/17 - 5/17 - 4/17=3/17

a)\(\frac{2}{5}+\frac{3}{4}=\frac{8}{20}+\frac{15}{20}=\frac{23}{20}\)
b)\(\frac{7}{12}-\frac{2}{7}+\frac{1}{12}=\frac{7}{12}+\frac{1}{12}-\frac{2}{7}\)\(=\frac{8}{12}-\frac{2}{7}=\frac{56}{84}-\frac{24}{84}=\frac{32}{84}=\frac{8}{21}\)
c) \(\frac{12}{17}-\frac{5}{17}-\frac{3}{17}=\frac{12-5-3}{17}=\frac{4}{17}\)
Chúc bạn học tốt !