Tìm x: |x+4|.|x|=0 x^2=4 1+2+3+4+…+100+x=5050 |2x+4|=16 (2^4-4^2).100!+2020=x 3x+24=|85%-0,85|

0 bình luận về “Tìm x: |x+4|.|x|=0 x^2=4 1+2+3+4+…+100+x=5050 |2x+4|=16 (2^4-4^2).100!+2020=x 3x+24=|85%-0,85|”

1. `|x + 4| . |x| = 0`

   `=>` \(\left[ \begin{array}{l}|x + 4| = 0\\|x| = 0\end{array} \right.\) 
   `=>` \(\left[ \begin{array}{l}x + 4 = 0\\x=0\end{array} \right.\) 
   `=>` \(\left[ \begin{array}{l}x=-4\\x=0\end{array} \right.\) 

   `–`

   `x^2 = 4`

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

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

   `–`

   `1 + 2 + 3 + 4 + … + 100 + x = 5050`

   `=> (x + 1) . [(x – 1) : 1 + 1] : 2 = 5050`

   `=> (x + 1) . x : 2 = 5050`

   `=> (x + 1) . x = 5050 . 2`

   `=> (x + 1) . x = 10100`

   `=> (x + 1) . x = 101 . 100`

   `=> x = 100`

   `–`

   `|2x + 4| = 16`

   `=>` \(\left[ \begin{array}{l}2x + 4 = 16\\2x + 4 = -16\end{array} \right.\) 
   `=>` \(\left[ \begin{array}{l}2x = 12\\2x=-20\end{array} \right.\) 
   `=>` \(\left[ \begin{array}{l}x=6\\x=-10\end{array} \right.\) 

   `–`

   `(2^4 – 4^2) . 100! + 2020 = x`

   `=> (16 – 16) . 100! + 2020 = x`

   `=> 0 . (1 . 2 . 3 . … . 100) + 2020 = x`

   `=> 0 + 2020 = x`

   `=> x = 2020`

   `–`

   `3x + 24 = |85% – 0,85|`

   `=> 3x + 24 = |0,85 – 0,85|`

   `=> 3x + 24 = 0`

   `=> 3x = 0 – 24`

   `=> 3x = -24`

   `=> x = -24 : 3`

   `=> x = -8`

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2. Đáp án:

   +`x=0;x=-4`

   + `x=4;x=-4`

   +`x=100`

   +$\left \{ {{x=6} \atop {x=-10}} \right.$ 

   +`x=2020`

   +`x=-8`

   Giải thích các bước giải:

   *`|x+4|.|x|=0`
   `=>|x+4|=0;|x|=0`
   `**|x+4|=0`
   `=>x+4=0`
   `x=0-4`
   `x=-4`
   `**|x|=0`
   `=>x=0`
   Vậy `x=0;x=-4`

   *`x^2=4`
   `=>x^2=4^2` hoặc `x^2=(-4)^2`(mũ chẵn có 2 đáp số)

   `=>x=4` hoặc `x=-4`
   Vậy `x=4;x=-4`

   `1+2+3+4+…+100+x=5050`
   `{(x+1).[(x-1):1+1]}/2=5050`
   `{(x+1).[x-1+1]}/2=5050`
   `[(x+1).x]/2=5050`
   `(x+1).x=5050.2`
   `(x+1).x=10100`
   `(x+1).x=101.100`
   `=>`\(\left[ \begin{array}{l}x+1=101\\x=100\end{array} \right.\) `=>x=100`
   Vậy `x=100`
   *`|2x+4|=16`
   `=>`\(\left[ \begin{array}{l}2x+4=16\\2x+4=-16\end{array} \right.\)`=>` \(\left[ \begin{array}{l}2x=16-4\\2x=(-16)-4\end{array} \right.\) `=>`\(\left[ \begin{array}{l}2x=12\\2x=-20\end{array} \right.\)`=>` \(\left[ \begin{array}{l}x=12:2\\x=(-20):2\end{array} \right.\) `=>`\(\left[ \begin{array}{l}x=6\\x=-10\end{array} \right.\) 
   Vậy \(\left[ \begin{array}{l}x=6\\x=-10\end{array} \right.\) 

   *`(2^4-4^2).100!+2020=x`
   `(16-16).100!+2020=x`
   `0.100!+2020=x`
   `0+2020=x`
   `=>x=2020`
   Vậy `x=2020`

   *`3x+24=|85%-0,85|`
   `3x+24=|85/100-0,85|`
   `3x+24=|0,85-0,85|`
   `3x+24=|0|`
   `3x+24=0`
   `3x=0-24`
   `3x=(-24)`
   `x=(-24):3`
   `x=(-8)`
   Vậy `x=-8`

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