参考・概略です
●多いので式だけです
[6]
(1) ax-by-ay+bx
=ax+bx-ay-by
=x(a-b)-y(a-b)
=(a-b)(x-y)
(2) x²-xy-2y-4
=x²-4-xy-2y
=(x-2)(x+2)-y(x+2)
=(x+2){(x-2)-y}
=(x+2)(x-y-2)
[7]
(1) x²+xy-2y²+6x+8
=x²+xy+6x-2y²+8
=x²+(y+6)x-2(y²-4)
=x²+(y+6)z-2(y+2)(y-2)
={x+2(y+2)}{x-(y-2)}
=(x+2y+4)(x-y+2)
(2) 2x²-xy-y²+3y-2
=2x²-yx-(y²-3y+2)
=2x²-yx-(y-1)(y-2)
={2x+(y-2)}{x-(y-1)}
=(2x+y-2)(x-y+1)