Tìm `x` :
`a)`
`| x + 2| = 4`
`b)`
`(x + 2)^2 = 4`
`c)`
`(x + 3)^3 = 27`
Tìm `x` : `a)` `| x + 2| = 4` `b)` `(x + 2)^2 = 4` `c)` `(x + 3)^3 = 27`
By Piper
By Piper
Tìm `x` :
`a)`
`| x + 2| = 4`
`b)`
`(x + 2)^2 = 4`
`c)`
`(x + 3)^3 = 27`
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}`
`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`
`⇔` \(\left[ \begin{array}{l}x=0\\x=-3\end{array} \right.\)