If origin is the center of the Rhombus given, then the portion of the line x + 2 y = 4 that is in the first quadrant is one side of Rhombus.
The equation is : x/4 + y/2 = 1
so x axis intercept is 4 units and y axis intercept is 2 units.
The diagonal of the triangle formed by the x- and y intercepts of the line is the side of rhombus. It is equal to √(4²+2²) = 2√5 units
The vertices of the side are : (0, 2) and (4, 0)
From symmetry about the origin: the other two vertices are : (0, -2) and (-4, 0)