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\(a,\frac{1}{2}x+\frac{5}{2}=\frac{7}{2}x-\frac{3}{4}\)
\(\Leftrightarrow\frac{1}{2}x+\frac{5}{2}-\frac{7}{2}x=-\frac{3}{4}\)
\(\Leftrightarrow\frac{1}{2}x-\frac{7}{2}x+\frac{5}{2}=-\frac{3}{4}\)
\(\Leftrightarrow-3x+\frac{5}{2}=-\frac{3}{4}\)
\(\Leftrightarrow-3x=-\frac{13}{4}\)
\(\Leftrightarrow x=-\frac{13}{4}:(-3)=-\frac{13}{4}:\frac{-3}{1}=-\frac{13}{4}\cdot\frac{-1}{3}=\frac{13}{12}\)
\(b,\frac{2}{3}x-\frac{2}{5}=\frac{1}{2}x-\frac{1}{3}\)
\(\Leftrightarrow\frac{2}{3}x-\frac{2}{5}-\frac{1}{2}x=-\frac{1}{3}\)
\(\Leftrightarrow\frac{2}{3}x-\frac{1}{2}x-\frac{2}{5}=-\frac{1}{3}\)
\(\Leftrightarrow\frac{1}{6}x-\frac{2}{5}=-\frac{1}{3}\)
\(\Leftrightarrow\frac{1}{6}x=\frac{1}{15}\)
\(\Leftrightarrow x=\frac{1}{15}:\frac{1}{6}=\frac{1}{15}\cdot6=\frac{6}{15}=\frac{2}{5}\)
\(c,\frac{1}{3}x+\frac{2}{5}(x+1)=0\)
\(\Leftrightarrow\frac{1}{3}x+\frac{2}{5}x+\frac{2}{5}=0\)
\(\Leftrightarrow\frac{11}{15}x=-\frac{2}{5}\)
\(\Leftrightarrow x=-\frac{6}{11}\)
d,e,f Tương tự
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Đặt A=(1/2)^0+(1/2)^1+(1/2)^2+.............+(1/2)^20
suy ra 1/2A=(1/2)^1+(1/2)^2+(1/2)^3+..........+(1/2)^21
suy ra A-1/2A=[(1/2)^0+(1/2)^1+(1/2)^2+........+(1/2)^20]-[(1/2)^1+(1/2)^2+(1/2)^3+.........+(1/2)^21]
suy ra 1/2A=(1/2)^0-(1/2)^21
1/2A=1-(1/2)^21
A=[1-(1/2)^21]:1/2
A=[1-(1/2)^21].2
A=2-(1/2)^21.2
A=2-(1/2)^20
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a) \(\frac{81}{16}\)
b) \(\frac{-31}{8}\)
c) \(\frac{2417}{2401}\)
Bn làm đầy đủ ra giúp mik với !! Thầy mik bắt làm đầy đủ cơ !!!
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1,\(\text{|1-3x|=0}\)
=>\(1-3x=0\)
=>\(3x=0\)
=>\(x=0\)
Vậy...
2,\(\text{|}1+x\text{|}+\text{|}x-\dfrac{1}{3}\text{|}=0\)
=>\(1+x=0\)và \(x-\dfrac{1}{3}=0\)
=>\(x=-1\) và \(x=\dfrac{1}{3}\)
=> x thuộc rỗng
các câu sau tương tự
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2) Ta có: \(\hept{\begin{cases}\left|x+1\right|\ge0\\\left|x+2\right|\ge0\\\left|x+3\right|\ge0\end{cases}}\left(\forall x\right)\Rightarrow\left|x+1\right|+\left|x+2\right|+\left|x+3\right|\ge0\)
\(\Rightarrow2x\ge0\Rightarrow x\ge0\)
Phá ngoặc ta được: \(x+1+x+2+x+3=2x\)
\(\Leftrightarrow3x+6=2x\)
\(\Rightarrow x=6\)
Vậy x = 6
Đoạn cuối xin lỗi cho sửa lại:
\(3x+6=2x\)
\(\Leftrightarrow3x-2x=-6\)
\(\Rightarrow x=-6\)
Mà \(x\ge0\)
=> PT vô nghiệm
1 + 1 = 2
2 + 0 - 1 + 1 * 2 = 3
Hok tốt
^^
1+1=2
2+0-1+1*2=3
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