Question

Tìm x thuộc Z, biết :

A) 11 + ( 15 - x ) = 1

B) 2x - 35 = 15

C) 2 | x + 5 | = 12

Answer 1

a) 11+(15-x)=1

⇔15-x=-10

hay x=25

Vậy: x=25

b) 2x-35=15

⇔2x=50

hay x=25

Vậy: x=25

c) 2|x+5|=12

⇔|x+5|=6

\(\Leftrightarrow\left[{}\begin{matrix}x+5=6\\x+5=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-11\end{matrix}\right.\)

Vậy: x∈{1;-11}

Answer 2

A/ \( 11+(15-x)=1\)\(\Leftrightarrow11+15-x=1\Leftrightarrow x=11+15-1=25\)

KL: ...........

B/ \(2x-35=15\Leftrightarrow2x=15+35=50\Leftrightarrow x=25\)

KL: ............

C/ \(2\left|x+5\right|=12\Leftrightarrow\left|x+5\right|=6\Leftrightarrow\left[{}\begin{matrix}x+5=6\\x+5=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-11\end{matrix}\right.\)

KL: .............