x^2+2xy-8y^2+2x+14y-3
=(x-2y+3)(x+4y-1)
:x^2+2xy-8y^2=(x-2y)(x+4y)
x^2+2x-3=(x+3)(x-1)
-8y^2+14y-3=(-2y+3)(4y-1)