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![](https://rs.olm.vn/images/avt/0.png?1311)
a)
\(A=2+4+8+...+2048\)
\(A=2+2^2+...+2^{11}\)
\(2A=2^2+2^3+...+2^{12}\)
\(2A-A=\left(2^2+2^3+...+2^{12}\right)-\left(2+2^2+...+2^{11}\right)\)
\(A=2^{12}-2\)
a) 2+4+8+16+32+64+128+512+1024+2048
b thì minh cha ra. Mình sẽ cố làm ra b mong ban thong cam va bạn nho k đung cho minh nha
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2+4+8+16+...+1024+2048=2\left(1+2+4\right)+16\left(1+2+4\right)+128\left(1+2+4\right)+1024\left(1+2\right)=\left(2+16+128+1024\right)\left(1+2+4\right)+3072=1022+3072=4094\)
![](https://rs.olm.vn/images/avt/0.png?1311)
A = 2+4+8+16+...+1024+2048
=> A = 2 + 22 + 23 + ... + 211
=> 2A = 22 + 23 + 24 ... + 212
=> 2A - A = 22 + 23 + 24 ... + 212 - 2 + 22 + 23 + ... + 211
=> A = 212 - 2
![](https://rs.olm.vn/images/avt/0.png?1311)
Đặt \(A=1-\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-..-\frac{1}{2048}\)
\(\Rightarrow A=1-\left(1-\frac{1}{2}\right)-\left(\frac{1}{2}-\frac{1}{4}\right)-..-\left(\frac{1}{1024}-\frac{1}{2048}\right)\)
\(\Rightarrow A=1-1+\frac{1}{2}-\frac{1}{2}+\frac{1}{4}-..-\frac{1}{1024}+\frac{1}{2018}\)
\(\Rightarrow A+\frac{1}{2018}\)
1-1/2-1/4-1/8-1/16-1/32-1/64-1/128-1/256-1/512-1/1024-1/2048 =0.00048828125
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(x+\frac{1}{2}\right)+\left(x+\frac{1}{4}\right)+\left(x+\frac{1}{8}\right)+\left(x+\frac{1}{16}\right)=1\)
\(\Rightarrow\left(x+x+x+x\right)+\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}\right)=1\)
\(\Rightarrow4x+\frac{15}{16}=1\)
\(\Rightarrow4x=\frac{1}{16}\)
\(\Rightarrow x=\frac{1}{64}\)
Bài làm:
Xét: \(101\times102-101\times101-50-51=101\times\left(102-101\right)-101=101\times1-101=0\)
\(\Rightarrow\left(1+2+4+8+...+512\right)\times\left(101\times102-101\times101-50-51\right)=0\)
\(\Rightarrow\frac{\left(1+2+4+8+...+512\right)\times\left(101\times102-101\times101-50-51\right)}{2+4+8+16+...+1024+2048}=0\)
Học tốt!!!!