Toán Lớp 7: a) ║2x – 1║ = ║ x – 2 ║
b) ║2x -1║ + 4 = 3x
║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║
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Toán Lớp 7: a) ║2x – 1║ = ║ x – 2 ║
b) ║2x -1║ + 4 = 3x
║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║
Comments ( 2 )
Giải đáp:
Lời giải và giải thích chi tiết:
|2x-1|=|x-2|
$⇒\left[\begin{matrix} 2x-1=x-2\\ 2x-1=-(x-2)\end{matrix}\right.$
$⇒\left[\begin{matrix} 2x-x=1-2\\ 2x-1=-x+2\end{matrix}\right.$
$⇒\left[\begin{matrix} 2x-x=1-2\\ 2x+x=1+2\end{matrix}\right.$
$⇒\left[\begin{matrix} x=-1\\ 3x=3\end{matrix}\right.$
$⇒\left[\begin{matrix} x=-1\\ x=1\end{matrix}\right.$
Vậy x in {-1;1}
b)|2x-1|+4=3x
=>|2x-1|=3x-4
$⇒\left[\begin{matrix} 2x-1=3x-4\\ 2x-1=-(3x-4)\end{matrix}\right.$
$⇒\left[\begin{matrix} 2x-3x=1-4\\ 2x-1=-3x+4\end{matrix}\right.$
$⇒\left[\begin{matrix} 2x-3x=1-4\\ 2x+3x=1+4\end{matrix}\right.$
$⇒\left[\begin{matrix}-1x=-3\\ 5x=1+4\end{matrix}\right.$
$⇒\left[\begin{matrix}x=3\\ x=1\end{matrix}\right.$
Vậy x in {3;1}
Giải đáp+Lời giải và giải thích chi tiết:
a)
|2x – 1| = | x – 2 |
=>\(\left[ \begin{array}{l}2x – 1=x – 2\\2x – 1=2-x\end{array} \right.\)
=>\(\left[ \begin{array}{l}2x -x= – 2+1\\2x+x =2+1\end{array} \right.\)
=>\(\left[ \begin{array}{l}x= -1\\3x =3\end{array} \right.\)
=>\(\left[ \begin{array}{l}x= -1\\x =1\end{array} \right.\)
Vậy x=±1
b)
|2x -1| + 4 = 3x với x>=4/3
=>|2x -1| = 3x-4
=>\(\left[ \begin{array}{l}2x -1=3x-4\\2x -1=4-3x\end{array} \right.\)
=>\(\left[ \begin{array}{l}2x -3x=-4+1\\2x +3x=4+1\end{array} \right.\)
=>\(\left[ \begin{array}{l}-x=-3\\5x=5\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=3(TM)\\x=1(KTM)\end{array} \right.\)
Vậy x=3