9x²+6x-y²+4y-3
=9x²+6x+1-y²+4y-4
=9x²+6x+1-(y²-4y+4)
=(3x+1)²-(y-2)²
=[(3x+1)-(y-2)][(3x+1)+(y-2)]
=(3x+1-y+2)(3x+1+y-2)
=(3x-y+3)(3x+y-1)
x²+5xy+x+3y+6y²
=x²+5xy+6y² +x+3y
=(x+2y)(x+3y)+(x+3y)
=(x+3y)(x+2y+1)
3x²-2x-2y²-4y-xy
=3x²-xy-2y²-2x-4y
=(3x+y)(x-2y)-2(x+2y)
=(3x+y-2)(x-2y)