a, (x+5)+(x-9)=x+2
\(\Leftrightarrow\)(x+5)+(x-9)-x-2=0
\(\Leftrightarrow\)x+5+x-9-x-2=0
\(\Leftrightarrow\)x-6=0
\(\Leftrightarrow\)x=6
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b, \(\left|x+3\right|\)+\(\left|x+2\right|\)=x
\(\Leftrightarrow\)x+3+x+2=x
\(\Leftrightarrow\)x+3+x+2-x=0
\(\Leftrightarrow\)x+5=0
\(\Leftrightarrow\)x=-5
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c, 2.\(\left|x-20\right|\)=10
\(\Leftrightarrow\)\(\left|x-20\right|\)=5
\(\Leftrightarrow\)\(\left[\begin{matrix}x-20=5\\x-20=-5\end{matrix}\right.\)
\(\Leftrightarrow\)\(\left[\begin{matrix}x=25\\x=15\end{matrix}\right.\)
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d, 2.\(\left|x-5\right|\)=2\(^5\)
\(\Leftrightarrow\)2.\(\left|x-5\right|\)=32
\(\Leftrightarrow\)\(\left|x-5\right|\)=16
\(\Leftrightarrow\)\(\left[\begin{matrix}x-5=16\\x-5=-16\end{matrix}\right.\)
\(\Leftrightarrow\)\(\left[\begin{matrix}x=21\\x=-11\end{matrix}\right.\)
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e, -5x+(7-15)=-6x+5
\(\Leftrightarrow\)-5x-8=-6x+5
\(\Leftrightarrow\)-5x-8+6x-5=0
\(\Leftrightarrow\)x-13=0
\(\Leftrightarrow\)x=13
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f, 23-3.\(\left|2x+6\right|\)=-7
\(\Leftrightarrow\)3.\(\left|2x+6\right|\)=30
\(\Leftrightarrow\)\(\left|2x+6\right|\)=10
\(\Leftrightarrow\)\(\left[\begin{matrix}2x+6=10\\2x+6=-10\end{matrix}\right.\)
\(\Leftrightarrow\)\(\left[\begin{matrix}x=2\\x=-8\end{matrix}\right.\)
Vậy...
Chúc bạn học tốt!!!^^^
