32-2.(x+1)=42
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H9
HT.Phong (9A5)
CTVHS
22 tháng 6 2023
\(A=\dfrac{1}{3}+\dfrac{1}{3^2}+\dfrac{1}{3^3}+\dfrac{1}{3^4}+...+\dfrac{1}{3^{99}}\)
\(\Rightarrow\dfrac{A}{3}=\dfrac{1}{3^2}+\dfrac{1}{3^3}+\dfrac{1}{3^4}+...+\dfrac{1}{3^{100}}\)
\(\Rightarrow A-\dfrac{A}{3}=\dfrac{2A}{3}=\left(\dfrac{1}{3}+\dfrac{1}{3^2}+\dfrac{1}{3^3}+...+\dfrac{1}{3^{99}}\right)-\left(\dfrac{1}{3^2}+\dfrac{1}{3^3}+\dfrac{1}{3^4}+...+\dfrac{1}{3^{100}}\right)\)
\(\Rightarrow\dfrac{2A}{3}=\left(\dfrac{1}{3^2}-\dfrac{1}{3^2}\right)+\left(\dfrac{1}{3^3}-\dfrac{1}{3^3}\right)+...+\left(\dfrac{1}{3^{99}}-\dfrac{1}{3^{99}}\right)+\left(\dfrac{1}{3}-\dfrac{1}{3^{100}}\right)=\dfrac{1}{3}-\dfrac{1}{3^{100}}\)
\(\Rightarrow2A=3\cdot\left(\dfrac{1}{3}-\dfrac{1}{3^{100}}\right)\)
\(\Rightarrow\text{A}=\dfrac{1-\dfrac{1}{3^{99}}}{2}\)
\(\Rightarrow A=\dfrac{1}{2}-\dfrac{1}{2.3^{99}}< \dfrac{1}{2}\)
9 tháng 12 2018
32-2.(x+1)=42
2.(x+1)=42+32
2.(x+1)=74
x+1=74:2
x+1=37
x=37-1
x=36
chúc bạn hok tốt
NV
Nguyễn Việt Lâm
Giáo viên
14 tháng 12 2018
\(42-2\left(32-2^{x+1}\right)=10\)
\(\Leftrightarrow2\left(32-2^{x+1}\right)=42-10=32\)
\(\Leftrightarrow32-2^{x+1}=16\)
\(\Leftrightarrow2^{x+1}=32-16=16\)
\(\Leftrightarrow2^{x+1}=2^4\)
\(\Leftrightarrow x+1=4\)
\(\Rightarrow x=3\)
CT
3
16 tháng 12 2018
\(42-2\left(32-2^{x+1}\right)=10\)
\(\Leftrightarrow2^{x+1}=16\)
\(\Leftrightarrow2^{x+1}=2^4\)
=> x = 4
16 tháng 12 2018
\(42-2.\left(32-2^{x+1}\right)=10\)
\(2.\left(32-2^{x+1}\right)=42-10\)
\(2.\left(32-2^{x+1}\right)=32\)
\(32-2^{x+1}=32:2\)
\(32-2^{x+1}=16\)
\(2^{x+1}=32-16\)
\(2^{x+1}=16\)
\(2^{x+1}=2^4\)
\(x+1=4\)
\(x=4-1\)
\(x=3\)
T
14 tháng 12 2023
\(a,[(2\cdot x-11):3+1]\cdot5=20\\\Rightarrow (2x-11):3+1=20:5\\\Rightarrow (2x-11):3+1=4\\\Rightarrow (2x-11):3=4-1\\\Rightarrow (2x-11):3=3\\\Rightarrow2x-11=3\cdot3\\\Rightarrow2x-11=9\\\Rightarrow2x=9+11\\\Rightarrow2x=20\\\Rightarrow x=20:2=10\)
\(b,(25-2x)^3:5-3^2=4^2\\\Rightarrow(25-2x)^3:5-9=16\\\Rightarrow(25-2x)^3:5=16+9\\\Rightarrow(25-2x)^3:5=25\\\Rightarrow(25-2x)^3=25\cdot5\\\Rightarrow(25-2x)^3=125\\\Rightarrow(25-2x)^3=5^3\\\Rightarrow25-2x=5\\\Rightarrow2x=25-5\\\Rightarrow2x=20\\\Rightarrow x=20:2=10\\Toru\)
9 tháng 12 2021
\(2,\)
\(a,20-\left[4^2+\left(x-6\right)\right]=90\)
\(\Rightarrow20-16-x+6=90\)
\(\Rightarrow10-x=90\)
\(\Rightarrow x=-80\)
Vậy: \(x=-80\)
\(b,\left(x+3\right)\left(2x-4\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x+3=0\\2x-4=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=-3\\x=2\end{matrix}\right.\)
Vậy: \(x\in\left\{-3;2\right\}\)
\(c,1000:\left[30+\left(2^x-6\right)\right]=3^2+4^2\left(x\in N\right)\)
\(\Rightarrow1000:\left(30+2^x-6\right)=25\)
\(\Rightarrow24+2^x=40\)
\(\Rightarrow2^x=16\)
\(\Rightarrow x=4\)
Vậy: \(x=4\)
\(32-2\left(x+1\right)=42\)
\(\Rightarrow32-2x-1=42\)
\(\Rightarrow31-2x=42\)
\(\Rightarrow2x=31-42\)
\(\Rightarrow2x=-11\)
\(\Rightarrow x=\frac{-11}{2}\)
\(\Rightarrow x=-5,5\)
32-2.(x+1)=42
=>2.(x+1)=32-42
=>2.(x+1)=-10
=>x+1=-10:2
=>x+1=-5
=>x=-5-1
=>x=-6