因式分解（3m²-n²）-（m²-3n²）²要过程

因式分解（3m²-n²）-（m²-3n²）²要过程

(3m²-n²)²-(m²-3n²)²
用平方差公式
(3m²-n²)²-(m²-3n²)²
=[(3m²-n²)-(m²-3n²)] [(3m²-n²) + (m²-3n²)]
= [2 (m²+n² )] [4 m²-4 n²]
= [2 (m²+n²)] [ 4( m- n) (m+n)]
= 8 ( m- n) (m+n) (m²+n² )

有没有写错呀，前面一个是不是少一个平方呀