Rewrite this as x^2-4x+4 + 9(y^2-8y+16)-4-144+139; (x-2)^2+9(y-4)^2=9. This is the equation of an ellipse with origin at (2,4). It can be written: (x-2)^2/3^2+(y-4)^2=1. The lengths of the semi-axes are 1 and 3. The shape of the ellipse is that it's wider than it's tall. To draw it treat the point (2,4) as a displaced origin and then on either side of this origin mark 1 unit up (positive) and unit down (negative) on the displaced y axis, and 3 units left and right on the displaced x axis. The ellipse extends no higher or lower than the points on the displaced y axis nor no further left or right than the points on the displaced x axis. You can see that the horizontal major axis is 6 units long and the vertical minor axis is 2 units long.