add (4x^2 - 8xy + y^2) + (-8x^2 - 9xy - y^2) + (x^2 + xy - 8y^2)

Question

adding powers.

Answer 1

(4x ^2 - 8xy + y^2) + (- 8x ^2 - 9xy -y ^2) + (x^2 + xy - 8y ^2)

= 4x^2 - 8xy + y ^2 - 8x ^2 - 9xy -y ^2 + x ^2 + xy - 8y ^2

= - 3x ^2 - 16xy - 8y ^2.