Question

Pt đa thức thành NT :

câu 15 : -x mũ 2 + 6x + 6y + y mũ 2

Answer 1

\(-x^2+6x+6y+y^2\\=-(x^2-6x+9)+(y^2+6y+9)\\=-(x-3)^2+(y+3)^2\\=(y+3)^2-(x-3)^2\\=[(y+3)-(x-3)][(y+3)+(x-3)]\\=(y+3-x+3)(y+3+x-3)\\=(y-x+6)(x+y)\)