Question

Tìm \(x\in Z\) biết :

a) \(\left(x+4\right)\left(x.x+1\right)=0\)

b) \(\left(\left|x\right|+2\right)\left(x.x-1\right)=0\)

Chúc các bn học tốt!!

Answer 1

a) \(\left(x+4\right)\left(x\cdot x+1\right)=0\)

\(\Rightarrow\left(x+4\right)\left(x^2+1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x+4=0\\x^2+1=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-4\\x\notin R\end{matrix}\right.\)

\(\Rightarrow x=-4\)

Vậy \(x=-4\)

b) \(\left(\left|x\right|+2\right)\left(x\cdot x-1\right)=0\)

\(\Rightarrow\left(\left|x\right|+2\right)\left(x^2-1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}\left|x\right|+2=0\\x^2-1=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x\in\varnothing\\x=1\\x=-1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=-1\\x=1\end{matrix}\right.\)

Vậy \(x_1=-1;x_2=1\)

Answer 2

Tìm x \(\in\)Z

a) (x+4)(x.x+1)=0

(x+4)(x²+1)=0

<=>x+4 và x²+1=0

Nếu x+4=0=>x=-4

Nếu x²+1=0=>x²=-1(ko có giá tri)

Vậy...

b)(|x|+2)(x.x-1)=0

(|x|+2)(x²-1)=0

<=>|x|+2 và x²-1=0

+|x|+2=0=>|x|=-2(không tồn tại)

+x²-1=0=>x²=1=>x={1;-1}

Vậy....

Answer 3

a)\(\left(x+4\right)\left(x\cdot x+1\right)=0\)

\(\Rightarrow\left(x+4\right)\left(x^2+1\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x+4=0\\x^2+1=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=-4\\x\in\varnothing\end{matrix}\right.\)

\(\Rightarrow x=-4\)

Vậy \(x=-4\).

b)\(\left(\left|x\right|+2\right)\left(x\cdot x-1\right)=0\)

\(\Rightarrow\left(\left|x\right|+2\right)\left(x^2-1\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}\left|x\right|+2=0\\x^2-1=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x\in\varnothing\\x=1\\x=-1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=1\\x=-1\end{matrix}\right.\)

Vậy \(x\in\left\{1;-1\right\}\).