Answer:
3x ^ 2 + 12x-36 = 0
3(x²+ 4x-12)=0
3(x²-2x+6x-12)=0
3[x(x-2)+6(x-2)]=0
3(x-2)(x+6)=0
⇒[tex]\left \{ {{x-2=0} \atop {x+6=0}} \right.[/tex]⇔[tex]\left \{ {{x=2} \atop {x=-6}} \right.[/tex]
