a) x²+4x+3=0
(=)x²+x+3x+3=0
(=)x(x+1)+3(x+1)=0
(=)(x+3)(x+1)=0
(=)\(\left[ \begin{array}{l}x+3=0\\x+1=0\end{array} \right.\) (=)\(\left[ \begin{array}{l}x=-3\\x=-1\end{array} \right.\)
S={-3;-1}
b) x²-x-12=0
(=)x²+3x-4x-12=0
(=)x(x+3)-4(x+3)=0
(=)(x-4)(x+3)=0
(=)\(\left[ \begin{array}{l}x-4=0\\x+3=0\end{array} \right.\)(=) \(\left[ \begin{array}{l}x=4\\x=-3\end{array} \right.\)
S={4;-3}
c) x²-3x+2=0
(=)x²-x-2x+2
(=)x(x-1)-2(x-1)=0
(=)(x-2)(x-1)=0
(=)\(\left[ \begin{array}{l}x-2=0\\x-1=0\end{array} \right.\)(=)\(\left[ \begin{array}{l}x=2\\x=1\end{array} \right.\)
S={2;1}
d) -x²+5x-6=0
(=)-x²+2x+3x-6=0
(=)-x(x-2)+3(x-2)=0
(=)(3-x)(x-2)=0
(=)\(\left[ \begin{array}{l}3-x=0\\x-2=0\end{array} \right.\) (=)\(\left[ \begin{array}{l}x=3\\x=2\end{array} \right.\)
S={3;2}
