Answer :

-2x+0 is perpendicular to -2x+4y=12, and go through (0,0).
So the answer is -2x+0
-2x+4y=12 <=> y = (-1/2)x + 3 => the slope of given line is -1/2;

the new line and the given line are perpendicular =>( the slope of new line )*(-1/2) = -1 =>

the slope of new line is 2;

the equation of the new line is y -0  =2( x -0) <=> y = 2x.