x^2-2xy-8y^2-14y-6-x
=(x+ay+b)(x+cy+d)
=x^2+(a+c)xy+ac*y^2+(a+c)y+(b+d)x+bd
a+c=-2
ac=-8
bc+ad=-14
b+d=-1
bd=-6
a=2,b=2,c=-4,d=-1
x^2-2xy-8y^2-14y-6-x
=(x+2y+2)(x-4y-3)