（3a-5b）²-（3a+5b）²=?
问题描述：
（3a-5b）²-（3a+5b）²=?
答
（3a-5b）²-（3a+5b）²
=[(3a-5b)+(3a+5b)][(3a-5b)-(3a+5b)]
=6a*(-10b)
=-60ab