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\(A=\dfrac{20}{35\cdot31}+\dfrac{30}{35\cdot41}+\dfrac{45}{41\cdot50}+\dfrac{35}{50\cdot57}\)
=5(4/31*35+6/35*41+9/41*50+7/50*57)
=5(1/31-1/35+1/35-1/41+1/41-1/50+1/50-1/57)
=5*(1/31-1/57)
=130/1767
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\(\frac{5}{7}\times x=\frac{20}{35\times31}+\frac{30}{35\times41}+\frac{45}{50\times41}+\frac{35}{50\times57}\)
\(\frac{5}{7}\times x=5\times\left(\frac{4}{35\times31}+\frac{6}{35\times41}+\frac{9}{50\times41}+\frac{7}{50\times57}\right)\)
\(\frac{5}{7}\times x=5\times\left(\frac{1}{31}-\frac{1}{35}+\frac{1}{35}-\frac{1}{41}+\frac{1}{41}-\frac{1}{50}+\frac{1}{50}-\frac{1}{57}\right)\)
\(\frac{5}{7}\times x=5\times\left(\frac{1}{31}-\frac{1}{57}\right)\)
\(x=5\times\frac{26}{1767}:\frac{5}{7}\)
\(x=7\times\frac{26}{1767}\)
\(x=\frac{182}{1767}\)
Vậy \(x=\frac{182}{1767}\)
Nếu thấy đúng thì cho mình vài cái h đúng nha!!!
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1> a) \(\frac{5}{7}x4:\frac{5}{9}=\frac{5}{7}:\frac{5}{9}x4=\frac{5}{7}x\frac{9}{5}x4=\frac{9}{7}x4=\frac{9x4}{7}=\frac{36}{7}\)
\(b,8x\frac{2}{3}:\frac{1}{2}=8x\frac{2}{3}x\frac{2}{1}=8x2x\frac{2}{3}=16x\frac{2}{3}=\frac{32}{3}\)
\(c,6:\frac{3}{5}-\frac{7}{6}x\frac{6}{7}=6x\frac{5}{3}-1=10-1=9\)
\(\frac{21}{5}x\frac{10}{11}+\frac{57}{11}=\frac{42}{11}+\frac{57}{11}=\frac{99}{11}=9\)
2) a) \(\frac{35}{9}:x=\frac{35}{6}\)
\(x=\frac{35}{9}:\frac{35}{6}\)
\(x=\frac{35}{9}x\frac{6}{35}\)
\(x=\frac{2}{3}\)
b) \(\left(\frac{1}{1x2}+\frac{1}{2x3}+\frac{1}{3x4}+\frac{1}{4x5}+\frac{1}{5x6}\right)x10-X=0\)
\(\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+.....+\frac{1}{5}-\frac{1}{6}\right)x10-X=0\)
\(\left(\frac{1}{1}-\frac{1}{6}\right)x10-X=10\)
\(\frac{5}{6}x10-X=0\)
\(X=\frac{5}{6}x10=\frac{25}{3}\)
Đúng nha !!!!
1/a/\(\frac{5}{7}\cdot4:\frac{5}{9}=\frac{20}{7}:\frac{5}{9}=\frac{20}{7}\cdot\frac{9}{5}=\frac{36}{7}\)
b/\(8\cdot\frac{2}{3}:\frac{1}{2}=\frac{16}{3}:\frac{1}{2}=\frac{16}{3}\cdot\frac{2}{1}=\frac{32}{3}\)
c/\(6:\frac{3}{5}-\frac{7}{6}\cdot\frac{6}{7}=6\cdot\frac{5}{3}-1=10-1=9\)
2/a/\(\frac{35}{9}:x=\frac{35}{6}\)
\(x=\frac{35}{9}:\frac{35}{6}=\frac{35}{9}\cdot\frac{6}{35}\)
\(x=\frac{2}{3}\)
b/\(\left(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}\right)\cdot10-x=0\)
\(\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}\right)\cdot10-x=0\)
\(\left(\frac{30}{60}+\frac{10}{60}+\frac{5}{60}+\frac{2}{30}\right)\cdot10-x=0\)
\(\frac{47}{60}\cdot10-x=0\)
\(\frac{47}{6}-x=0\)
\(x=\frac{47}{6}-0\)
\(x=\frac{47}{6}\)
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1/ X : 1/7 + 1/7 = 8/9
X : 1/7 = 8/9 -1/7
X : 1/7 = 47/63
X = 47/63 x 1/7
X = 47/441
2/ X : ( 1/7 + 6/7 ) = 8/9
X : 1 = 8/9
X = 8/9 x1
X = 8/9
3/ 1/7 : ( X + 4/7 ) = 13/5
X + 4/7 = 1/7 : 13/5
X + 4/7 = 5/91
X = 5/91 - 4/7
X = -49/91
4/ 3/7 : ( X - 1/9) = 4/5
X - 1/9 = 3/7 : 4/5
X -1/9 = 15/28
X = 15/28 + 1/9
X = 163/252
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bài toán = 17819/2520 nha
đề dài nên tính máy cho nhanh
ht
1/2 +2/3 + 3/4 + 4/5 + 5/6 + 6/7 + 7/8 + 8/9 + 9/10 x ( 3/4 x 8/6 ) : ( 1/5 : 1/5 )
= 1/2 + 2/3 + 3/4 + 4/5 + 5/6 + 6/7 + 7/8 + 8/9 + 9/10 x 1
= 17819/2520
HT~
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a) \(23\times57+42\times23+23=23\times\left(57+42+1\right)\)
\(=23\times100=2300\)
b) \(\frac{2}{9}\times\frac{5}{7}+\frac{2}{9}\times\frac{2}{7}=\frac{2}{9}\times\left(\frac{5}{7}+\frac{2}{7}\right)\)
\(=\frac{2}{9}\times1=\frac{2}{9}\)
a) 23 x 57 + 42 x 23 + 23
= 23 x ( 57 + 42 + 1 )
= 23 x 100
= 2300
b) \(\frac{2}{9}\times\frac{5}{7}+\frac{2}{9}\times\frac{2}{7}\)
\(=\frac{2}{9}\times\left(\frac{5}{7}+\frac{2}{7}\right)\)
\(=\frac{2}{9}\times1\)
\(=\frac{2}{9}\)
Học tốt #
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sao chả có ai giải bài hộ bạn thế bạn giải giúp mik với đang cần gấp
Quyền đây
=>x*5/57=130/1767
=>x=26/31