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1/1.2+1/2.3+1/3.4+......+1/99.100
=1-1/2+1/2-1/3+1/3-1/4+..........+1/99-1/100
=1-1/100
=99/100
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\(\frac{1}{1.2}+\frac{1}{2.3}+....+\frac{1}{99.100}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\)
\(=1-\frac{1}{100}=\frac{99}{100}\)
=1/1.2+1/2.3+..+1/99.100
=1-1/3+1/2-1/3+.....+1/99-1/100
=1/100-1
=99/100
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S = 2/1×2 + 2/2×3 + 2/3×4 + 2/4×5 + ... + 2/101×102
B = 2 × (1/1×2 + 1/2×3 + 1/3×4 + 1/4×5 + ... + 1/101×102)
B = 2 × (1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + ... + 1/101 - 1/102)
B = 2 × (1 - 1/102)
B = 2 × 101/102
B = 101/51
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\(B=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{5.6}+...+\frac{1}{99.100}\)
\(B=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{99}-\frac{1}{100}\)
\(B=\frac{1}{2}-\frac{1}{100}=\frac{49}{100}\)
\(\Rightarrow B=\frac{49}{100}\)
mik viết nhầm nha bn, phải là 1/1.2 đầu tiên
bn biết làm thì giúp mik luôn nha
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a.6 +a = 420
a.7= 420
a= 420:7
a= 60
Vậy...
240 ( a . 3 + a . 5 ) = 2.3
240 ( a . 3 + a . 5 ) = 6
a.3 + a.5 = 240:6
a. 8 = 40
a= 40:8
a= 5
Vậy....
=2.(3+4+3)
=2.10
=20
tinh nhanh
2.3+2.4+2.3=?
\(=2.\left(3+4+3\right)\)
\(=2.10\)
\(=20\)