Đúng là hok sinh giỏi có khác ,bài toán nó cũng khó
Ta có:
\(p^{m+2}q-p^{m+1}q^3-p^2q^{n+1}+pq^{n+3}\)
\(=\left(p^{m+2}q-p^{m+1}q^3\right)-\left(p^2q^{n+1}-pq^{n+3}\right)\)
\(=p^{m+1}q\left(p-q^2\right)-pq^{n+1}\left(p-p^2\right)\)
\(=\left(p-p^2\right)\left(p^{m+1}q-pq^{n+1}\right)\)
\(=pq\left(p-p^2\right)\left(p^m-p^n\right)\)