∫(0.+∞)dx∫(x.2x)e∧(-y^2)dy
=∫(0.+∞)dy∫(y/2.y)e∧(-y^2)dx
=∫(0.+∞)ye∧(-y^2)/2dy
=∫(0.+∞)e∧(-y^2)/4dy^2
=-e^(-y^2)/4|(0.+∞)
=1/4