Find the distance between the parallel line and plane:
l: r=[2,0,1] + t[1,4,1]
pi: 2x - y + 2z = 4
Take any point on the line and calculate the distance from the plane:
Point on the line: (2,0,1)=(x0,y0,z0)
Distance from the plane:
D=(2x0-y0+2z0-4)/√(2²+(-1)²+2²)
=(4+0+2-4)/√(4+1+4)
=2/&radic(9)
=2/3