1. Take out the highest common factor from all terms.
4mn−16n2−4m2n+64n3=4n(m−4n−m2+16n2)
2. Rearrange the terms inside the bracket to expose a difference of squares.
4n(m−4n−m2+16n2)=4n{−(m2−16n2)+(m−4n)}
3. Factorise completely by grouping with the common factor $(m-4n)$.
4n{−(m2−16n2)+(m−4n)}=4n{−(m−4n)(m+4n)+(m−4n)}=4n(m−4n)(1−m−4n)=−4n(m−4n)(m+4n−1)答案−4n(m−4n)(m+4n−1)