输入m→平方→（-2m）→×m→+3m²→输出?
问题描述：
输入m→平方→（-2m）→×m→+3m²→输出?
答
(m²-2m)m+3m²
=m³-2m²+3m²
=m³+m²
输入m→平方→（-2m）→×m→+3m²→输出?
(m²-2m)m+3m²
=m³-2m²+3m²
=m³+m²