(a+b)^2-(a-b)^2
=(a+b-a+b)(a+b+a-b)
=2b*2a
=4ab
平方差公式变形(a+b）的平方-(a-b)的平方
(a+b)^2-(a-b)^2
=(a+b-a+b)(a+b+a-b)
=2b*2a
=4ab
(a+b)^2-(a-b)^2
=(a+b-a+b)(a+b+a-b)
=2b*2a
=4ab
(a+b)^2-(a-b)^2
=(a+b-a+b)(a+b+a-b)
=2b*2a
=4ab
(a+b)^2-(a-b)^2
=(a+b-a+b)(a+b+a-b)
=2b*2a
=4ab