tính nhanh
100 + 1000 + 10 + 1 + 10000
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=-(0,1+0,01+0,001+0,0001+0,00001)
=-0,11111
Đây là cách đơn giản nhất
B = \(-\frac{1}{10}-\frac{1}{100}-\frac{1}{1000}-...-\frac{1}{1000000}\)
B = \(-\left(\frac{1}{10}+\frac{1}{10^2}+\frac{1}{10^3}+...+\frac{1}{10^6}\right)\)
Đặt A = \(\frac{1}{10}+\frac{1}{10^2}+\frac{1}{10^3}+...+\frac{1}{10^6}\)
10A = \(1+\frac{1}{10}+\frac{1}{10^2}+...+\frac{1}{10^5}\)
9A = 10A - A = \(1-\frac{1}{10^6}\)
=> A = \(\frac{1-\frac{1}{10^6}}{9}\)
=> B = \(-\left(\frac{1-\frac{1}{10^6}}{9}\right)\)
C=(0,1+0,01+0,001+...+0,000001)=-0,111111
mình ko chép đề bài
\(\frac{1}{10}+\frac{20}{100}+\frac{300}{1000}+\frac{40000}{100000}\)
\(=\frac{1}{10}+\frac{20}{10}+\frac{30}{10}+\frac{40}{10}\)
\(=\frac{1+2+3+4}{10}\)
\(=\frac{10}{10}\)
\(=1\)
1/10 + 20/100 + 300/1000 + 4000/10000
=1/10 + 2/10 + 3/10 + 4/10
=10/10
=1
Bài làm
\(\frac{1}{10}+\frac{20}{100}+\frac{300}{1000}+\frac{4000}{10000}\)
\(=\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+\frac{4}{10}\)
\(=\frac{1+2+3+4}{10}\)
\(=\frac{10}{10}\)
\(=1\)
# Học tốt #
\(\frac{1}{10}+\frac{20}{100}+\frac{300}{1000}+\frac{4000}{10000}\)
=\(\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+\frac{4}{10}\)
= \(\frac{1+2+3+4}{10}\)
=\(\frac{10}{10}\)
= 1
Ta có : \(B=\frac{-1}{10}-\frac{1}{100}-\frac{1}{1000}-\frac{1}{10000}-\frac{1}{100000}\)
\(\Rightarrow B=-\left(\frac{1}{10}+\frac{1}{100}+\frac{1}{1000}+\frac{1}{10000}+\frac{1}{100000}\right)\)
Đặt \(A=\frac{1}{10}+\frac{1}{100}+\frac{1}{1000}+\frac{1}{10000}+\frac{1}{100000}\)
\(\Rightarrow10A=1+\frac{1}{10}+\frac{1}{100}+\frac{1}{1000}+\frac{1}{10000}\)
\(\Rightarrow10A-A=1-\frac{1}{100000}\)
\(\Rightarrow9A=\frac{99999}{100000}\)
\(\Rightarrow A=\frac{99999}{100000}.\frac{1}{9}=\frac{11111}{100000}\)
=> B = \(-\frac{11111}{100000}\)
\(A=\frac{-1}{10}-\frac{1}{100}-\frac{1}{1000}-\frac{1}{10000}-\frac{1}{100000}\)
\(\Rightarrow A=-\left(\frac{1}{10}+\frac{1}{100}+\frac{1}{1000}+\frac{1}{10000}+\frac{1}{100000}\right)\)
\(\Rightarrow A=-\left(\frac{10000}{100000}+\frac{1000}{100000}+\frac{100}{100000}+\frac{10}{100000}+\frac{1}{100000}\right)\)
\(\Rightarrow A=-\left(\frac{10000+1000+100+10+1}{100000}\right)\)
\(\Rightarrow A=-\left(\frac{11111}{100000}\right)\)
\(\Rightarrow A=\frac{-11111}{100000}\)
= 11111
100 + 1000 = 1100
1100+10=1110
1110+ 10000=11110
tk minh nha abn