Question 461614

(2x^2-2xy+y^2) + (-7x^2-3xy-y^2) + (x^2+xy-2y^2) 

= 2x^2-7x^2 +x^2 -2xy -3xy +xy + y^2 -y^2-2y^2

= -4x^2 -4xy -2y^2