Question 261620
Add.

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


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


{{{2x^2 - 7xy + y^2 - 6x^2 - 2xy - y^2 + x^2 + xy - 9y^2}}} ------ Distribute


{{{2x^2 - 6x^2 + x^2 - 7xy - 2xy + xy + y^2 - y^2 - 9y^2}}} 


{{{highlight_green(-3x^2 - 8xy - 9y^2)}}}