You can put this solution on YOUR website! The vertex of y = 6x^2 +3 is (0,3). The min is y = 3 because this is the y coordinate of the vertex and the leading coefficient is positive.
Domain: The set of all real numbers (this is true for any polynomial)
Range: The set of all real numbers such that (this is because the min is y = 3). Basically any number greater than or equal to 3 is part of the range.