(x - y + 7)(x + y)
That factors to y(y2 + 7y - 5)
y2+7y=18 y2+7y-18=0 (y+9)(y-2)=0 y=-9 & y=2
This is not factor-able.
(y + 7)(y + 7)
(x - y + 7)(x + y)
(y + 3)(y - 10)
(y - 8)(y + 1)
That factors to y(y2 + 7y - 5)
y2+7y=18 y2+7y-18=0 (y+9)(y-2)=0 y=-9 & y=2
This is not factor-able.
25x2 - 10xy + y2 = (5x - y)2
(y+2)(y+3)
(y + 7)(y + 7)
(y - 5)(y - 6)
(3x - y)(3x - y)
(y - 8)(y - 2)