1) ( x + 1) + ( x + 3) + ( x + 5) + ... + ( x + 99) = 0 2) x( x+ 3) = 0 3) ( x - 2) ( 5 - x) = 0 4) ( x - 1) ( x2 + 2) = 0

` Huy `

` a) (x+1)+(x+3)+(x+5)+...+(x+99)=0 `

` => (x+x+x+...+x)+(1+3+5+...+99)=0 `

` => 50x + 2500 = 0 `

` => 50x = -2500 `

` => x = -50 `

` b) x . (x+3) = 0 `

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

` c) (x-2).(5-x)=0 `

` => ` \(\left[ \begin{array}{l}x-2=0\\5-x=0\end{array} \right.\) 

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

` d) (x-1) . ( 2x+ 2 ) = 0 `

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

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