Question

simplify by combining like terms.
$9x^{2}-3xy - y^{2}+2x^{2}-xy + 2y^{2}$
$9x^{2}-3xy - y^{2}+2x^{2}-xy + 2y^{2}=\square$
(simplify your answer. do not factor.)

Explanation:

Step1: Group $x^2$ terms

$(9x^2 + 2x^2) - 3xy - y^2 - xy + 2y^2$

Step2: Combine $x^2$ terms

$11x^2 - 3xy - y^2 - xy + 2y^2$

Step3: Group $xy$ terms

$11x^2 + (-3xy - xy) - y^2 + 2y^2$

Step4: Combine $xy$ terms

$11x^2 - 4xy - y^2 + 2y^2$

Step5: Group $y^2$ terms

$11x^2 - 4xy + (-y^2 + 2y^2)$

Step6: Combine $y^2$ terms

$11x^2 - 4xy + y^2$

Answer:

$11x^2 - 4xy + y^2$