Question 238553
Solution set: (-5,-4) U (11, infinity)





(6x^2-9xy+y^2)+(-9x^2-7xy-y^2)+(x^2+xy+7y^2) 


(6x^2-9x^2+x^2)+(-9xy-7xy+xy)+(y^2-y^2+7y^2)


-2x^2-15xy+7y^2