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a: 5/9=40/72
7/8=63/72
b: 7/12=14/24
13/24=13/24
c: 9/16=18/32
17/32=17/32
d: 11/6=77/42
8/7=48/42
e: 5/6=20/24
11/24=11/24
f: 13/16=13/16
25/8=50/16
quy đồng mẫu số :
\(\frac{5}{8}=\frac{1105}{1768}\)
\(\frac{8}{13}=\frac{1088}{1768}\)
\(\frac{13}{17}=\frac{1352}{1768}\)
(MSC: 1768 )
học tốt
5/8=1106/1768
8/13=1088/1768
13/17=1352/1768
NHO K MINH VOI NHA
a) 3/4 ; 5/7 và 8/3
3/4 = 63/84
5/7 = 60/84
8/3 = 224/84
b) 5/8 ; 8/13 và 13/17
5/8 = 1105/1768
8/13 = 1088/1768
13/17 = 2496/1768
Chúc em học giỏi !
=>BCNN=84 =>BCNN=1768
\(\frac{3}{4}=\frac{3.21}{4.21}=\frac{63}{84}\) \(\frac{5}{8}=\frac{5.221}{8.221}=\frac{1105}{884}\)
\(\frac{5}{7}=\frac{5.12}{7.12}=\frac{60}{84}\) \(\frac{8}{13}=\frac{8.68}{13.68}=\frac{544}{884}\)
\(\frac{8}{3}=\frac{8.28}{3.28}=\frac{224}{84}\) \(\frac{13}{17}=\frac{13.52}{17.52}=\frac{676}{884}\)
\(\frac{17}{12}+\frac{3}{5}+\frac{19}{12}+\frac{8}{13}+\frac{2}{5}+\frac{18}{13}\)
\(=\left(\frac{17}{12}+\frac{19}{12}\right)+\left(\frac{8}{13}+\frac{18}{13}\right)+\left(\frac{3}{5}+\frac{2}{5}\right)\)
\(=3+2+1\)
\(=6\)
1) Ta có: \(\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{7}{25}\cdot\dfrac{5}{7}\right)\)
\(=\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{1}{5}\right)\)
=0
2) Ta có: \(\dfrac{8}{17}\cdot\dfrac{4}{15}+\dfrac{8}{17}\cdot\dfrac{22}{15}-\dfrac{8}{15}\cdot\dfrac{9}{17}\)
\(=\dfrac{8}{17}\left(\dfrac{4}{15}+\dfrac{22}{15}-\dfrac{9}{15}\right)\)
\(=\dfrac{8}{17}\cdot\dfrac{15}{15}=\dfrac{8}{17}\)
3) Ta có: \(\dfrac{2021}{2}\cdot\dfrac{1}{3}+\dfrac{4042}{4}\cdot\dfrac{1}{5}+\dfrac{6063}{3}\cdot\dfrac{22}{15}\)
\(=\dfrac{2021}{2}\left(\dfrac{1}{3}+\dfrac{1}{5}\right)+2021\cdot\dfrac{22}{15}\)
\(=\dfrac{2021}{2}\cdot\dfrac{8}{15}+\dfrac{2021}{2}\cdot\dfrac{44}{15}\)
\(=\dfrac{2021}{2}\cdot\dfrac{52}{15}\)
\(=\dfrac{52546}{15}\)
4) Ta có: \(\dfrac{4}{7}\cdot\dfrac{2}{13}+\dfrac{8}{13}:\dfrac{7}{4}+\dfrac{4}{7}:\dfrac{13}{2}+\dfrac{4}{7}\cdot\dfrac{1}{13}\)
\(=\dfrac{4}{7}\left(\dfrac{2}{13}+\dfrac{8}{13}+\dfrac{2}{13}+\dfrac{1}{13}\right)\)
\(=\dfrac{4}{7}\)
\(=\left(\frac{4}{17}+\frac{13}{17}\right)-\left(\frac{7}{15}+\frac{8}{15}\right)+\left(\frac{10}{16}-\frac{7}{16}\right)\)
\(=1-1+\frac{3}{16}\)
\(\frac{3}{16}\)
gộp 1,3
2,4
5,6
thì ra 17/17-15/15+3/16=3/16
hk tốt!