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\(1-\frac{1}{2}+2-\frac{2}{3}+3-\frac{3}{4}+4-\frac{1}{4}-3-\frac{1}{3}-2-\frac{1}{2}-1\)
\(\left(1-1\right)-\left(\frac{1}{2}+\frac{1}{2}\right)+\left(2-2\right)-\left(\frac{2}{3}+\frac{1}{3}\right)+\left(3-3\right)-\left(\frac{3}{4}+\frac{1}{4}\right)-1\)
\(-1-1-1+4=1\)
MIK XIN LỖI BN NHA VÌ ĐÁNH MÁY HƠI LÂU NHA !! CHÚC BN HOK TỐT NHAA
\(=1-\dfrac{1}{1+\dfrac{2}{1+1}}=1-\dfrac{1}{1+1}=1-\dfrac{1}{2}=\dfrac{1}{2}\)
\(a,A=\frac{-251489}{15750}\)
b,\(B=\frac{47}{12}\)
\(c,C=\frac{11}{25}\)
\(d,D=\frac{10}{39}\)
a) S=1 + 2 + 2^2 + 2^3 +...+ 2^63
2S=2 + 2^2 + 2^3 + 2^4 +...+ 2^64
S=2S-S=(2 + 2^2 + 2^3 + 6^4 +...+ 2^64)-(1 + 2 + 2^2 + 2^3 +...+ 2^63)
S=2 + 2^2 + 2^3 + 2^4 +...+ 2^64 - 1 - 2 - 2^2 - 2^3 -...- 2^63
S=2^64 - 1
Đặt: \(A=\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+..+\dfrac{1}{100}\)
\(\Rightarrow\dfrac{1}{A}=1:\left(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{100}\right)\)
\(\Rightarrow\dfrac{1}{A}=2+3+4+5+...+100\)
\(\Rightarrow\dfrac{1}{A}=\left(100+2\right)\cdot99:2\)
\(\Rightarrow\dfrac{1}{A}=5049\)
\(\Rightarrow A=\dfrac{1}{5049}\)
\(=\dfrac{1}{3}+\dfrac{1}{6}+\dfrac{1}{10}+...+\dfrac{1}{2021\cdot2022:2}\)
\(=2\left(\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+...+\dfrac{1}{2021\cdot2022}\right)\)
\(=2\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{2021}-\dfrac{1}{2022}\right)\)
\(=2\cdot\dfrac{505}{1011}=\dfrac{1010}{1011}\)