`a ) x . ( x+23)=0`
`<=>`\(\left[ \begin{array}{l}x=0\\x+23=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=0\\x=-23\end{array} \right.\)
Vậy `x€{0;-23}`
`b ) ( x-2) . (5 .x)=0`
`<=>`\(\left[ \begin{array}{l}x-2=0\\5x=0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=2\\x=0\end{array} \right.\)
Vậy `x€{0;2}`
`c ) ( x -3)-16= -4`
`<=>x-3=-4+16`
`<=>x-3=12`
`<=>x=15`
Vậy `x=15`
`d ) 26- (x +9) = -13`
`<=>26-x-9=-13`
`<=>15-x=-13`
`<=>x=28`
Vậy `x=28`
`Huyy`