a)
x²-3x=0
x(x-3)=0
x=0 ∨ x-3=0
x=3
b)
5x²+12x=0
x(5x+12)=0
x=0 ∨ 5x+12=0
5x=-12 |:5
x=-2 2/5
c)
6x²-216x=0
6x(x-36)=0
6x=0 ∨ x-36=0
x=0 ∨ x=36
