Now complete the squares:
4(x-2)²+9(y-2)²=0, which is not an ellipse. In fact it can only be satisfied when x=y=2, that is, the single point (2,2). To be an ellipse the constant 52 needs to be replaced or removed so that a strictly positive constant can follow the equals sign, and the constant must be less than 52. For example, 48 would create an ellipse, so that we have 4 after the equals. The smaller the constant, the larger the ellipse. The constant 52 causes the ellipse to collapse to a single point.