Question 381477
the line y=2x-6 can be seen as : (x,y)=(1,2)t+(0,-6), where t is a parameter, and (1,2) the vector describing the direction of the line
 
the 2nd equation is : y=-2x, or (x,y)=(1,-2)t
 
since both vector (1,2), (1,-2) are not co-linear, they are not parallel.
 
if we compute the dot product of both vector, we find (1,2)(1,-2)=1+4 different from 0, hence the lines are not perpendicular neither.