Rút gọn biểu thức:
A=1+1/2+1/2^2+1/2^3+...+1/2^2012
HELP ME , PLEASE
K
Khách
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26 tháng 2 2018
Ta có :
\(A=1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{2012}}\)
\(2A=1+2+\frac{1}{2}+...+\frac{1}{2^{2011}}\)
\(2A-A=\left(1+2+\frac{1}{2}+...+\frac{1}{2^{2011}}\right)-\left(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{2012}}\right)\)
\(A=2-\frac{1}{2^{2012}}\)
\(A=\frac{2^{2013}-1}{2^{2012}}\)
Vậy \(A=\frac{2^{2013}-1}{2^{2012}}\)
AM
10 tháng 6 2015
\(A=1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{2012}}\)
=>2A=\(2+1+\frac{1}{2}+...+\frac{1}{2^{2011}}\)
=>2A-A=\(\left(2+1+\frac{1}{2}+...+\frac{1}{2^{2011}}\right)-\left(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{2012}}\right)=2-\frac{1}{2^{2012}}\)
=>A=\(\frac{2^{2013}-1}{2^{2012}}\)
9 tháng 5 2017
ta có :
2.A=1/2+2/22+...+1/22013
2.A-A=(2+1+1/22+...+1/22011)-(1+1/2+1/22+...+1/22012)
=>A= 2-1/22012
9 tháng 5 2017
2A=2+1+1/2+1/2^2+...+1/2^2011
2A-A=A=(2+1+1/2+1/2^2+...+1/2^2011)-(1+1/2+1/2^2+...+1/2^2012)
A=2-1/2^2012
VP
1
13 tháng 5 2021
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29 tháng 10 2023
a: \(\left(2x+1\right)^2+\left(2x-1\right)^2-2\left(x-3\right)^2\)
\(=4x^2+4x+1+4x^2-4x+1-2\left(x^2-6x+9\right)\)
\(=8x^2+2-2x^2+12x-18\)
\(=6x^2+12x-16\)
b: \(\left(x-1\right)^2-\left(3x+2\right)^2\)
\(=x^2-2x+1-9x^2-12x-4\)
\(=-8x^2-14x-3\)
c: \(\left(6x+1\right)^2+\left(6x-1\right)^2-2\left(6x+1\right)\left(6x-1\right)\)
\(=\left(6x+1\right)^2-2\left(6x+1\right)\left(6x-1\right)+\left(6x-1\right)^2\)
\(=\left(6x+1-6x+1\right)^2=2^2=4\)
AD
2
Y
1 tháng 7 2023
\(A=2\sqrt{27}-\sqrt{\left(1-\sqrt{3}\right)^2}+\dfrac{1}{2-\sqrt{3}}\\ =2.3\sqrt{3}-\left|1-\sqrt{3}\right|+\dfrac{2+\sqrt{3}}{\left(2-\sqrt{3}\right)\left(2+\sqrt{3}\right)}\\ =6\sqrt{3}-\left(-1+\sqrt{3}\right)+\dfrac{2+\sqrt{3}}{2^2-\sqrt{3^2}}\\ =6\sqrt{3}+1-\sqrt{3}+2+\sqrt{3}\\ =6\sqrt{3}+3\)
LT
0
lộn kết quả rút gọn là \(2-\frac{1}{2^{2012}}\)nhé
tớ ghi lộn kết quả nhưng cách tính là đúng
k nhé
\(A=1+\frac{1}{2}+...+\frac{1}{2^{2012}}\)
\(\Rightarrow2A=2+1+...+\frac{1}{2^{2011}}\)
\(\Rightarrow2A-A=\left(2+1+...+\frac{1}{2^{2011}}\right)-\left(1+\frac{1}{2}+...+\frac{1}{2^{2012}}\right)\)
\(\Rightarrow A=2-\frac{1}{2^{2012}}\)
Chúc bạn học tốt !!!!