Bài 9: Tìm x ∈ Z biết: a) (x+3) (2 − x ) = 0 b) (2x − 5)² = 9 c) (1− 3 x)³ =8 d) (x +7) (8 − x) = 0 e) (x² +1) (49 − x² ) = 0 f) ( x + 2) (6 − 2 x) = 0 giúp mik vs ạ

Đáp án+Giải thích các bước giải:

`a)(x+3)(2-x)=0`

`=>`\(\left[ \begin{array}{l}x+3=0\\2-x=0\end{array} \right.\)

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

Vậy `x=-3` hoặc `x=2`

`b)(2x-5)^2=9`

`=>(2x-5)^2=3^2`

`=>`\(\left[ \begin{array}{l}2x-5=3\\2x-5=-3\end{array} \right.\) 

`=>`\(\left[ \begin{array}{l}2x=8\\2x=2\end{array} \right.\) 

`=>`\(\left[ \begin{array}{l}x=4\\x=1\end{array} \right.\) 

Vậy `x=4` hoặc `x=1`

`c)(1-3x)^3=8`

`=>(1-3x)^3=2^3`

`=>1-3x=2`

`=>3x=1-2`

`=>3x=-1`

`=>x=(-1)/3`

Vậy `x=(-1)/3`

`d)(x+7)(8-x)=0`

`=>`\(\left[ \begin{array}{l}x+7=0\\8-x=0\end{array} \right.\) 

`=>`\(\left[ \begin{array}{l}x=-7\\x=8\end{array} \right.\) 

Vậy `x=-7` hoặc `x=8`

`e)(x^2+1)(49-x^2)=0`

`=>`\(\left[ \begin{array}{l}x^2+1=0\\49-x^2=0\end{array} \right.\) 

`=>`\(\left[ \begin{array}{l}x^2=-1\\x^2=49\end{array} \right.\) 

`=>`\(\left[ \begin{array}{l}x^2=-1\\x^2=7^2\end{array} \right.\) 

`=>`\(\left[ \begin{array}{l}x^2=-1(vô lý)\\x=7\\x=-7\end{array} \right.\) 

Vậy `x=7` hoặc `x=-7`

`f)(x+2)(6-2x)=0`

`=>`\(\left[ \begin{array}{l}x+2=0\\6-2x=0\end{array} \right.\) 

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

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

Vậy `x=2` hoặc `x=-3`