`1) ``X²-5x+6=0`
`⇔(X-2)(x-3)=0`
⇔$\left \{ {{x-2=0} \atop {x-3=0}} \right.$
⇔$\left \{ {{x=2} \atop {x=3}} \right.$
2) $\left \{ {{2x+y=-14} \atop {x-y=5}} \right.$
$\left \{ {{3x=-9} \atop {x-y=5}} \right.$
$\left \{ {{x=-3} \atop {-3-y=5}} \right.$
$\left \{ {{x=-3} \atop {y=-8}} \right.$