Bài 1. Tìm x : 1/ ( 2x – 5 ) + 17 = 6. 2/ 10 – 2 ( 4 – 3x ) = – 4. 3/ – 12 + 3 ( – x + 7 ) = – 18. 4/ 24 : ( 3x – 2 ) = – 3. 5/ – 45 : 5 . ( – 3 – 2x

Bài 1. Tìm x :
1/ ( 2x – 5 ) + 17 = 6.
2/ 10 – 2 ( 4 – 3x ) = – 4.
3/ – 12 + 3 ( – x + 7 ) = – 18.
4/ 24 : ( 3x – 2 ) = – 3.
5/ – 45 : 5 . ( – 3 – 2x ) = 3.

Bài 2. Tìm x :
1/ x . ( x + 7 ) = 0
2/ ( x + 12 ) . ( x – 3 ) = 0.
3/ ( – x + 5 ) . ( 3 – x ) = 0.
4/ x . ( 2 + x ) . ( 7 – x ) = 0.
5/ ( x – 1 ) . ( x + 2 ) . ( – x – 3 ) = 0.

0 bình luận về “Bài 1. Tìm x : 1/ ( 2x – 5 ) + 17 = 6. 2/ 10 – 2 ( 4 – 3x ) = – 4. 3/ – 12 + 3 ( – x + 7 ) = – 18. 4/ 24 : ( 3x – 2 ) = – 3. 5/ – 45 : 5 . ( – 3 – 2x”

  1. Bài 1: Tìm x:
    1/ $( 2x – 5 ) + 17 = 6$ 
    ⇔ $2x – 5 + 17 = 6$ 
    ⇔ $2x + 12 = 6$ 
    ⇔ $2x = 6 – 12$
    ⇔ $2x = -6$
    ⇔ $x = ( – 6) ÷ 2$
    ⇔ $x = -3$

    2/ $10 – 2( 4 – 3x ) = -4$
    ⇔ $10 – ( 2.4 – 2.3x ) = -4$
    ⇔ $10 – 8 + 6x = -4$
    ⇔ $2 + 6x = -4$
    ⇔ $6x = -4-2$
    ⇔ $6x = -6$
    ⇔ $x = ( -6)÷6$
    ⇔ $x = -1$

    3/ $-12 + 3( -x + 7 ) = -18$
    ⇔$-12 -3x + 21 = -18$
    ⇔$9 – 3x = -18$
    ⇔ $-3x = -18 – 9$ 
    ⇔ $-3x = -27$
    ⇔ $x = 9$

    4/ $24 : ( 3x – 2)=-3$
    ⇔ $3x – 2 = 24÷(-3)$
    ⇔ $3x – 2 = -8$
    ⇔ $3x = -8 + 2$
    ⇔ $3x = -6$
    ⇔ $x = -2$

    5/ $-45 ÷ 5 . ( -3 – 2x ) = 3$
    ⇔ $27 + 18x = 3$
    ⇔ $18x = -24$
    ⇔ $x = \dfrac{-24}{18}$

    Bài 2: Tìm x
    1/ $x .(x+7)=0$
    ⇔ \(\left[ \begin{array}{l}x=0\\x+7=0\end{array} \right.\)
    ⇔ \(\left[ \begin{array}{l}x=0\\x=-7\end{array} \right.\)

    2/ $( x + 12 ). ( x – 3) = 0$ 
    ⇔ $\(\left[ \begin{array}{l}x+12=0\\x-3=0\end{array} \right.\)$ 
    ⇔ $\(\left[ \begin{array}{l}x=-12\\x=3\end{array} \right.\)$ 

    3/ $( -x + 5 ) .(3-x) = 0$
    ⇔ \(\left[ \begin{array}{l}-x+5=0\\3-x=0\end{array} \right.\)
    ⇔ \(\left[ \begin{array}{l}x=5\\x=3\end{array} \right.\) 

    4/ $x(2+x)(7-x)=0$
    ⇔ $x = 0;$      $2+x=0$ và     $7-x=0$
    ⇔ $x = 0$ ;     $x = -2$ và     $x = 7$

    5/ $( x -1)(x+2)(-x-3)=0$
    ⇔ $x -1 = 0$;   $x+2=0$    và     $-x-3=0$
    ⇔ $x = 1$;    $x =-2$     và      $x = -3$

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  2. Đáp án:

     Bài `1`

    ` 1)`

    ` (2x -5) + 17 = 6 `

    ` 2x -5 +17= 6`

    ` 2x +12 = 6`

    ` 2x= -6`

    ` x =-3`

    `2)`

    ` 10 – 2(4-3x) = -4`

    ` 10 – 8 + 6x + 4 = 0`

    ` 6x + 6 = 0`

    ` 6x = -6`

    ` x= -1`

    `3)`

    ` -12 + 3(-x+7) = -18`

    ` 3(-x+7) = -6`

    ` – x +7 = -2`

    ` -x = -9`

    `

    ` x = 9`

    `4)`

    ` 24 : (3x-2) = -3`

    ` 3x -2  = -8`

    ` 3x = -6`

    ` x = -2`

    `5)`

    ` -45 : 5(-3 -2x) = 3`

    ` 5(-3x-2) = -15`

    ` -3x -2 = -3`

    ` -3x = -1`

    ` x = 1/3`

    Bài `2`

    ` 1)`

    ` => ` \(\left[ \begin{array}{l}x=0\\x+7=0\end{array} \right.\) 

    `=>` \(\left[ \begin{array}{l}x=0\\x=-7\end{array} \right.\) 

    `2)`

    ` => ` \(\left[ \begin{array}{l}x+12=0\\x-3=0\end{array} \right.\) 

    ` =>` \(\left[ \begin{array}{l}x=-12\\x=3\end{array} \right.\) 

    `3)`

    ` => ` \(\left[ \begin{array}{l}-x+5=0\\3-x=0\end{array} \right.\) 

    ` =>` \(\left[ \begin{array}{l}x=5\\x=3\end{array} \right.\) 

    `4)`

    ` => x = 0`

    hoặc ` 2 + x = 0` hoặc ` 7 – x = 0`

    ` => x = 0` hoặc ` x = -2 ; x =7`

    `5)`

    ` => x -1 = 0` hoặc ` x +2 = 0` hoặc ` -x-3 = 0`

    ` => x =1` ; ` x = -2 ;  x = 3`

     

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