Comment résoudre (6x2 + 11xy - 11y2) + (3x2 - 5xy - 8y2) ?

(6x^2 + 11xy - 11y^2) + (3x^2 - 5xy - 8y^2)
  = x^2(6+3) + xy(11-5) + y^2(-11-8)
  = 9x^2 + 6xy - 19y^2

(6x^2 + 11xy - 11y^2) + (3x^2 - 5xy - 8y^2)
= (6x^2 + 3x^2) + (11xy - 5xy) + (-11y^2 - 8y^2)
= 9x^2 + 6xy - 19y^2

La question est
(6x ² +11xy- 11y ² ) - (3x ² - 5xy - 8y ² )
expansion
6x ² +11xy - 11y ² -3x ² +5xy+8y ²
addition de termes similaires
6x ² +16xy- 11y ² -3x ² +8y ²
soustraction de termes similaires :
3x ² +16xy-3y ²