câu1 a 5. (x-7) = 7. (x-3) b3. (x-8)-6.(x-5)=12 c7.(x-4)-3.(x+8)=-84 d 6. (x-3)=8.(x-4) e 19-|2x+3|=-6 câu 2 3x+4y-xy=15

0 bình luận về “câu1 a 5. (x-7) = 7. (x-3) b3. (x-8)-6.(x-5)=12 c7.(x-4)-3.(x+8)=-84 d 6. (x-3)=8.(x-4) e 19-|2x+3|=-6 câu 2 3x+4y-xy=15”

1. $a, 5.(x-7)=7.(x-3)$

   $⇔5x-35=7x-21$

   $⇔5x-7x=-21+35$

   $⇔-2x=14$

   $⇔x=-7$

   $b,3.(x-8)-6.(x-5)=12$

   $⇔3x-24-6x+30=12$

   $⇔-3x=12+24-30$

   $⇔-3x=6$

   $⇔x=-2$

   $c,7.(x-4)-3.(x+8)=-84$

   $⇔7x-28-3x-24=-84$

   $⇔4x=-32$

   $⇔x=-8$

   $d,6.(x-3)=8.(x-4)$

   $⇔6x-18=8x-32$

   $⇔-2x=-14$

   $⇔x=7$

   $e,19-|2x+3|=-6$

   $⇔19-2x-3=-6$

   $⇔-2x=-22$

   $⇔x=11$

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2. `\text{~~Holi~~}`

   `1.`

   `a. 5(x-7)=7(x-3)`

   `-> 5x-35=7x-21`

   `-> 5x-7x=-21+35`

   `-> -2x=14`

   `-> x=(14)/(-2)`

   `-> x=-7`

   Vậy `x=-7`

   `b. 3(x-8)-6(x-5)=12`

   `-> 3x-24-6x+30=12`

   `-> 3x-6x=12+24-30`

   `-> -3x=6`

   `-> x=6/(-3)`

   `-> x=-2`

   Vậy `x=-2`

   `c. 7(x-4)-3(x+8)=-84`

   `-> 7x-28-3x-24=-84`

   `-> 7x-3x=-84+28+24`

   `-> 4x=-32`

   `-> x=(-32)/4`

   `-> x=-8`

   Vậy `x=-8`

   `d. 6(x-3)=8(x-4)`

   `-> 6x-18=8x-32`

   `-> 6x-8x=-32+18`

   `-> -2x=-14`

   `-> 2x=14`

   `-> x=7`

   `e. 19-|2x+3|=-6`

   `-> |2x+3|=19-(-6)`

   `-> |2x+3|=25`

   `-> 2x+3=±25`

   `->`\(\left[ \begin{array}{l}2x+3=25\\2x+3=-25\end{array} \right.\) 

   `->`\(\left[ \begin{array}{l}x=11\\x=-14\end{array} \right.\) 

   Vậy `x\in{11;-14}`

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