x^2-y^2+10x-6y-9
=x^2+10x -(y^2+6y+9)
= x^2+10x-(y^2+2.3.y+3^2)
=x^2+10x-(y+3)^2
=\(\left[x^2-\left(y+3\right)^2\right]+10x \)
={\(\left(x+x+3\right)\left[x-\left(x+3\right)\right]\)}\(+10x\)
=\(\left(x+x+3\right).\left(x-x-3\right)+10x\)
(đến đây b tự lm nhé, m cx k bt đúng k nx )