5-(10-x)=7
10-x=5-7
10-x=-2
x=10-(-2)
x=12
Vậy x=12
(4x-2)(x+5)=0
\(\left[ \begin{array}{l}4x-2=0\\x+5=0\end{array} \right.\)
\(\left[ \begin{array}{l}x=(0+2):4\\x=0-5\end{array} \right.\)
\(\left[ \begin{array}{l}x=1/2\\x=-5\end{array} \right.\)
Vậy x ∈{-5,1/2}
2x-9=-8-9
2x-9=-17
2x=-17+9
2x=-8
x=-8:2
x=-4
Vậy x=-4
3.|x-1|-27=0
3|x-1|=0+27
3|x-1|=27
|x-1|=27:3
|x-1|=9
\(\left[ \begin{array}{l}x-1=9\\x-1=-9\end{array} \right.\)
\(\left[ \begin{array}{l}x=9+1\\x=-9+1\end{array} \right.\)
\(\left[ \begin{array}{l}x=10\\x-8\end{array} \right.\)
Vậy x∈{10,-8}
