Find the equation of the tangent plane to the surface z=x2+2xy+y2z = x^2 + 2xy + y^2z=x2+2xy+y2 at the point (1,1,4)(1, 1, 4)(1,1,4).
z=4x+4y−4z = 4x + 4y - 4z=4x+4y−4
z=2x+2y−2z = 2x + 2y - 2z=2x+2y−2
z=4x+4y−3z = 4x + 4y - 3z=4x+4y−3
z=3x+3y−2z = 3x + 3y - 2z=3x+3y−2