We have to complete two squares here, one for x and one for y. Begin by rewriting:
2[x2 + 12x + ___ ] + 7[y2 + 12y + ___ ] = -310. Now, we complete each square and balance:
2[x2 + 12x + 36 ] + 7[y2 + 12y + 36 ] = -310 + 72 + 252
2(x + 6)2 + 7(y + 6)2 = 14 Divide both sides by 14
(x + 6)2 / 7 + (y + 6)2 / 2 = 1 Is an ellipse oriented horizontally, centered at (-6 , -6), with a = √7 , b = √2 , c = √5