Tìm `x` : `a)` `| x + 2| = 4` `b)` `(x + 2)^2 = 4` `c)` `(x + 3)^3 = 27`

0 bình luận về “Tìm `x` : `a)` `| x + 2| = 4` `b)` `(x + 2)^2 = 4` `c)` `(x + 3)^3 = 27`”

1. Đáp án:

   `a,S={-6;2}`

   `b, S={-4;0}`

   `c,S={0}`

    

   Giải thích các bước giải:

   `a, |x+2|=4`

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

   `=>`\(\left[ \begin{array}{l}x=2\\x=-6\end{array} \right.\) 

   Vậy `S={-6;2}`

   `b, (x+2)²=4`

   `=> (x+2)²=±2`

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

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

   Vậy `S={-4;0}`

   `c, (x+3)³=27`

   `=> (x+3)³=3³`

   `=> x+3=3`

   `=> x=0`

   Vậy `S={0}`

   Bình luận

2. `a ) | x + 2 | = 4 ⇔ x + 2 = ±4`

   `⇔` \(\left[ \begin{array}{l}x+2=4\\x+2=-4\end{array} \right.\)

   `⇔` \(\left[ \begin{array}{l}x=2\\x=-6\end{array} \right.\)

   `b ) ( x + 2 )^2 = 4`

   `⇔ ( x + 2)(x + 2) = 4`

   `⇔ x(x + 2) + 2(x + 2) = 4`

   `⇔ x^2 + 4x + 4 = 4`

   `⇔ x^2 + 4x = 0`

   `⇔ (x + 0)(x + 4) = 0`

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

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

   `c ) (x + 3)^3 = 27`

   `⇔( x + 3 ) = 3`

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

    

   Bình luận