因式分解!!幫下手

4x^2-36z^2-28xy+49y^2
= (4x^2 - 28xy + 49y^2) - 36z^2
= [(2x)^2 - 2(2x)(7y) + (7y)^2] - (6z)^2
= (2x - 7y)^2 - (6z)^2
= (2x - 7y - 6z) (2x - 7y + 6z)

樓上知唔知咩叫因識分解架