`a, = 5(x^2-2xy+y^2-4z^2)`
`= 5((x-y)^2 - 4z^2)`
`= 5((x-y+z)(x-y-z))`.
`b, (x+y)(x^2-xy+y^2) -(x+y)`
`= (x+y)(x^2-xy+y^2-1)`.
`c, (2x+1)^2 - y^2`
`= (2x+1-y)(2x+1+y)`
a,=5(x2−2xy+y2−4z2)a,=5(x2-2xy+y2-4z2)
=5((x−y)2−4z2)=5((x-y)2-4z2)
=5((x−y+z)(x−y−z))=5((x-y+z)(x-y-z)).
b,(x+y)(x2−xy+y2)−(x+y)b,(x+y)(x2-xy+y2)-(x+y)
=(x+y)(x2−xy+y2−1)=(x+y)(x2-xy+y2-1).
c,(2x+1)2−y2c,(2x+1)2-y2
=(2x+1−y)(2x+1+y)