2x^2-12x=0, factor x in 2x(x-6)=0, to have two possible roots of the equation I.e. x=0, +6. By plugging in the 6 as a possible root ignoring zero (0) we find that 2.6^2-12.6=0, then 2.36-12.6=0, 72-72=0 proving x as a root is correct and the other root has the same effect.