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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
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1+1+2+2+3+3+4+4+5+5+6+6+7+7+8+9+8+9+10+12+13+14+15+16+17+18+19+20+30+1000000=10000274
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\(=\left(\frac{14}{5}-\frac{4}{5}\right)+\left(\frac{7}{13}+\frac{19}{13}\right)+\left(\frac{17}{9}-\frac{8}{9}\right)\)
\(=\frac{10}{5}+\frac{26}{13}+\frac{9}{9}=2+2+1=5\)
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a)=(3/8+10/16)+(7/12+10/24)
=1+1=2
c)=(4/6+14/6)+(7/13+19/13)+(17/9+1/9)
=3+2+2=7
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bạn ơi bạn bị sai mất 2 câu cuối rồi đó làm ơn tính lại giùm mình nha
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\(\frac{14}{5}+\frac{9}{13}+\frac{17}{13}-\frac{8}{9}+\frac{17}{9}-\frac{4}{5}\)
\(=\left(\frac{14}{5}-\frac{4}{5}\right)+\left(\frac{9}{13}+\frac{17}{13}\right)+\left(\frac{17}{9}-\frac{8}{9}\right)\)
\(=2+2+1\)
\(=5\)
\(\frac{14}{5}+\frac{9}{13}+\frac{17}{13}-\frac{8}{9}+\frac{17}{9}-\frac{4}{5}\)
\(=\left(\frac{14}{5}-\frac{4}{5}\right)+\left(\frac{9}{13}+\frac{17}{13}\right)-\left(\frac{8}{9}-\frac{17}{9}\right)\)
\(=\frac{10}{5}+\frac{26}{13}-\left(-1\right)\)
\(=2+2+1\)
\(=5\)
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a) \(\dfrac{4}{6}+\dfrac{7}{13}+\dfrac{17}{9}-\dfrac{8}{9}+\dfrac{14}{6}+\dfrac{19}{13}\)
\(=\dfrac{2}{3}+\dfrac{7}{13}+\dfrac{17}{9}-\dfrac{8}{9}+\dfrac{7}{3}+\dfrac{19}{13}\)
\(=\left(\dfrac{2}{3}+\dfrac{7}{3}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)+\left(\dfrac{17}{9}-\dfrac{8}{9}\right)\)
\(=\dfrac{9}{3}+\dfrac{26}{13}+\dfrac{9}{9}\)
\(=3+2+1\)
\(=6\)
b) \(\dfrac{328}{435}\times\dfrac{468}{432}\times\dfrac{435}{164}\times\dfrac{432}{984}\times\dfrac{164}{468}\)
\(=\dfrac{328\times468\times435\times432\times164}{435\times432\times164\times984\times468}\)
\(=\dfrac{328}{984}\)
\(=\dfrac{1}{3}\)
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1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10=55
2 + 4 + 6 + 8 + 10 + 12 + 14 + 16 + 18 + 20=110
1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19=100
k mk nha pạn hiền!
10 +1 = 11 có 10 số vậy thì 10 : 2 = 5 thì sẽ bằng 5x11 = 55
2 + 20 = 22 cũng có 10 số lấy 10 : 2 = 5 se bang 22 x5 = 110
1+19 = 20 , 10 : 2 = 5 , 20x5 = 100
=(14/5-4/5)+(7/13+19/13)+(17/9-8/9)
=2+2+1=5