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1) x = 378; 756; 1134; 1512; 1890
2) x = 60; 120 ; 180 ; 240 ; 300 ; 360 ; 420 ; 480
3) x = 50 ; 100 ; 150 ; 200 ; 250 ; 300 ; 350 ; 400
4) x = 56;112;168;224; 280; 336; 392; 448;504;560;616;672
\(\left|x-1\right|+\left|x-3\right|+\left|x-5\right|+\left|x-7\right|=\left(\left|x-1\right|+\left|x-7\right|\right)+\left(\left|x-3\right|+\left|x-5\right|\right)\\ \)
\(=\left(\left|x-1\right|+\left|7-x\right|\right)+\left(\left|x-3\right|+\left|5-x\right|\right)\)
\(\ge\left|x-1+7-x\right|+\left|x-3+5-x\right|=\left|6\right|+\left|2\right|=8\)
\(\left|x+1\right|+\left|x+3\right|+\left|x+5\right|=\left(\left|x+1\right|+\left|x+3\right|\right)+\left|x+5\right|=\left(\left|x+1\right|+\left|3-x\right|\right)+\left|x+5\right|\)
\(\ge\left|x+1+3-x\right|+\left|x+5\right|=\left|4\right|+\left|x+5\right|=4+\left|x+5\right|\ge4\)
\(\left|x-1\right|+2\left|x-3\right|+\left|x-5\right|=\left(\left|x-1\right|+\left|x-5\right|\right)+2\left|x-3\right|=\left(\left|x-1\right|+\left|5-x\right|\right)+2\left|x-3\right|\)
\(\ge\left|x-1+5-x\right|+2\left|x-3\right|=\left|4\right|+2\left|x-3\right|=4+2\left|x-3\right|\ge4\)
=> 1/2.2/3.3/4...x/(x+1)=1/2009
=> 1/(x+1)=1/2009
=> x+1=2009
=> x=2008
Mik nhanh nhất mik nha
=> 1/2 . 2/3 . 3/4 .... x/x+1 = 1/2009
<=> (1.2.3...x) / [2.3...x.(x+1)] = 1/2009
<=> 1/ (x+1) = 1/2009
=> x+1=2009 => x=2008
\(2x\left(x-\frac{1}{7}\right)=0\)
=> 2x=0 hoặc x-1/7=0
=> x=0 hoặc x=1/7
\(\left|x\right|-2,2=1,2\)
=> |x|=1,2+2,2
=> |x|=3,4
=> x \(\in\){-3,4; 3,4}
\(\left|x+\frac{3}{4}\right|-\left|-\frac{1}{3}\right|=0\)
=> |x+3/4|-1/3=0
=> |x+3/4|=1/3
=> x+3/4=1/3 hoặc x+3/4=-1/3
=> x=1/3-3/4 hoặc x=-1/3-3/4
=> x=-5/12 hoặc x=-13/12
1/
\(A\)dương \(\Leftrightarrow\)\(\hept{\begin{cases}\left(x-\frac{1}{2}\right)>0\\x-\frac{4}{5}>0\end{cases}}\)
\(\Leftrightarrow\hept{\begin{cases}x>0+\frac{1}{2}\\x>0+\frac{4}{5}\end{cases}}\)
\(\Leftrightarrow\hept{\begin{cases}x>\frac{1}{2}\\x>\frac{4}{5}\end{cases}}\Leftrightarrow x>0,8\)
2/ Làm tương tự nhưng có 2 trường hợp nên bạn làm từng trường hợp nhé ..!
a) (2x+3)-(5x-17)=9
2x+3-5x+17=9
-3x+20=9
-3x=9-20=-11
=>x=11/3
b) \(\left(\frac{1}{5}+\frac{4}{5}x\right)-\left(\frac{2}{5}x+\frac{1}{9}\right)=\frac{3}{7}\)
=> \(\frac{1}{5}+\frac{4}{5}x-\frac{2}{5}x-\frac{1}{9}=\frac{3}{7}\)
=> \(\left(\frac{1}{5}-\frac{1}{9}\right)+\left(\frac{4}{5}x-\frac{2}{5}x\right)=\frac{3}{7}\)
\(\frac{4}{45}+\frac{2}{5}x=\frac{3}{7}\)
\(\frac{2}{5}x=\frac{3}{7}-\frac{4}{45}=\frac{107}{315}\)
x=107/315:2/5=107/126
