12) X/186=(1-303030/313131)+(616161/626262-1)+(929292/939393-1)
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\(\frac{\left|x\right|}{186}=\left(1-\frac{303030}{313131}\right)+\left(\frac{616161}{626262}-1\right)+\left(\frac{929291}{939393}-1\right)\)
<=> \(\frac{\left|x\right|}{186}=-\frac{303030}{313131}+\frac{616161}{626262}+\frac{929292}{939393}+1-1-1\)
<=> \(\frac{\left|x\right|}{186}=-\frac{30}{31}+\frac{61}{62}+\frac{92}{93}+1-1-1\)
<=> \(\frac{\left|x\right|}{186}=\frac{61}{62}+\frac{92}{93}-1-\frac{30}{31}\)
<=> \(\frac{\left|x\right|}{186}=-\frac{1.31}{31}+\frac{61}{62}+\frac{92}{91}-\frac{30}{31}\)
Lấy MSC là 168, ta có:
<=> \(\frac{\left|x\right|}{186}=\frac{-186}{186}+\frac{183}{186}+\frac{184}{186}-\frac{180}{186}\)
<=> \(\frac{\left|x\right|}{186}=\frac{-186+183+184-180}{186}\)
<=> \(\frac{\left|x\right|}{186}=\frac{1}{186}\)
<=> |x| = 1
<=> \(\orbr{\begin{cases}x=1\\x=-1\end{cases}}\)
=> \(\orbr{\begin{cases}x=1\\x=-1\end{cases}}\)
x/186 = (1 - 303030/313131) + (616161/626262 - 1) + (929292/939393 - 1)
x/186 = 1 - 30/31 + 61/62 - 1 + 92/93 - 1
x/186 = 61/62 - 30/31 + 92/93 - 1
x/186 = 1/62 - 1/93
x/186 = 1/186
x = 1
\(1-\frac{303030}{313131}+\frac{616161}{626262}-1+\frac{929292}{939393}-1=\left(1-\frac{30}{31}\right)+\left(\frac{61}{62}-1\right)+\left(\frac{92}{93}-1\right)\)
\(=\frac{1}{31}-\frac{1}{62}-\frac{1}{93}=\frac{1}{186}\)
=> \(\frac{\left|x\right|}{186}=\frac{1}{186}\)=> |x| = 1 => x = 1 hoặc x = - 1
Vậy...............
\(\frac{|x|}{186}=\left(1-\frac{30}{31}\right)+\left(\frac{60}{61}-1\right)\)
\(\Leftrightarrow|x|=186\left(\frac{1}{31}-\frac{1}{61}\right)\)
\(\Leftrightarrow|x|=6-\frac{186}{61}\)
\(\Leftrightarrow|x|=\frac{180}{61}\)
\(\Leftrightarrow x=\pm\frac{180}{61}\)
a ) | x + 1/3 | = 5/6
+) x + 1/3 = 5/6 hay x + 1/3 = -5/6
x = 5/6 - 1/3 x = -5/6 - 1/3
x = 1/2 x =-7/6
b ) 11/13 - ( 5/42 - x ) = - ( 15/28-11/13 )
11/13 - ( 5/42 - x ) = 113/364
( 5/42 - x ) = 11/13 - 113/364
( 5/42 - x ) = 15/28
x = 5/42 - 15/28
x = -5/12
c ) | x |/186 = ( 1 - 303030 / 313131 ) + ( 616161 / 626262 - 1 )
| x | / 186 = 1/62
| x | = 1/62 . 186
| x | = 3
x = 3 hoặc -3
\(\dfrac{x}{186}=\left(1-\dfrac{3030}{3131}\right)+\left(\dfrac{6161}{6262}-1\right)+\left(\dfrac{929292}{939393}-1\right)\\ \dfrac{x}{186}=\left(1-\dfrac{30}{31}\right)+\left(\dfrac{61}{62}-1\right)+\left(\dfrac{92}{93}-1\right)\\ \dfrac{x}{186}=\dfrac{1}{31}+\dfrac{-1}{62}+\dfrac{-1}{93}\\ \dfrac{x}{186}=\dfrac{6}{186}+\dfrac{-3}{186}+\dfrac{-2}{186}\\ \dfrac{x}{186}=\dfrac{1}{186}\\ \Rightarrow x=1\\ \Rightarrow\left|x\right|=1\)
Vậy \(\left|x\right|=1\)
A = \(\dfrac{9292\times939393}{929292\times9393}\) + 1,1 + 1,2 + 1,3 + ...+8,8 + 8,9 + 9
A = \(\dfrac{92\times101\times93\times10101}{92\times10101\times93\times101}\) + (1,1 + 9)\(\times\){(9 - 1,1):0,1 + 1}:2
A = 1 + 10,1\(\times\)80:2
A = 1 + 404
A = 405