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1x8=8
2x9=18
3x1+3x3+3x1+3x3+1
= 3x( 1+3+1+3)+1
=3x8+1
=24+1=25
1 +1+1+1+1+1+1+1=8
2+2+2+2+2+2+2+2+2=18
3 +3x3+3+3x3 x3 +1 =43
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1 + 1 + 1 + 1 + 1 - 5 + 2 + 2 + 2 + 2 + 2 - 10 + 1 - 1 + 0
= 1 x 5 - 5 + 2 x 5 - 10 + 1 - 1 + 0
= 5 - 5 + 10 - 10 + 1 - 1 + 0
= 0 + 10 - 10 + 1 - 1 + 0
= 10 - 10 + 1 - 1 + 0
= 0 + 1 - 1 + 0
= 1 - 1 + 0
= 0 + 0
= 0
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1+2+1+2+1+2+1+2+1+2
=>1×5+2×5
=5+10
=15
hoặc
=3+3+3+3+3
=6+6+3
=12+3
=15
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Cm 1/2 mu 2 - 1/ 2mu 4 + 1/ 2 mu 6-...-1/2mu 4n -2 -1/2 mu 4n + ...+ 1/ 2 mu 2014 - 1/ 2 mu 2016<0,2
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\(A=\frac{1}{2^2}-\frac{1}{2^4}+\frac{1}{2^6}-...+\frac{1}{2^{2014}}-\frac{1}{2^{2016}}\)
\(\Rightarrow2^2A=1-\frac{1}{2^2}+\frac{1}{2^4}-\frac{1}{2^6}+\frac{1}{2^8}-...+\frac{1}{2^{2012}}-\frac{1}{2^{2014}}\)
\(\Rightarrow2^2A+A=1+\left(\frac{1}{2^2}-\frac{1}{2^2}\right)+\left(\frac{1}{2^4}-\frac{1}{2^4}\right)+...+\left(\frac{1}{2^{2014}}-\frac{1}{2^{2014}}\right)-\frac{1}{2^{2016}}\)
\(\Rightarrow5A=1-\frac{1}{2^{2016}}< 1\Rightarrow A< \frac{1}{5}=0,2\)
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1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 2 + 2 + 2 + 9 + 10 = 41
chúc bn hok tốt ~
t mk nha
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\(\frac{1}{1^2}+\frac{1}{2^2}+\frac{1}{3^2}+...+\frac{1}{50^2}\)
\(< 1+\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{49.50}\)
\(=1+\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{49}-\frac{1}{50}\)
\(=2-\frac{1}{50}< 2\)
Vế trái =VT
\(VT< 1+\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\)
\(VT< 1+\frac{2-1}{1x2}+\frac{3-2}{2x3}+\frac{4-3}{3x4}+...+\frac{50-49}{49x50}\)
\(VT< 1+1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}=2-\frac{1}{50}< 2\)
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2 : 1 = 2
tick tớ nhé , tớ đầu tiên nha Đồ Tình Hàm
2
tick nhé bn thuộc bảng cửu chương chưa