(a-b)(3a+b)²+(a+3b)²(b-a)
=(a-b)(3a+b)²+-(a+3b)²(a-b)
=(a-b)[(3a+b)²-(a+3b)²]
=(a-b)(3a+b+a+3b)(3a+b-a-3b)
=(a-b)(4a+4b)(2a-2b)
=8(a-b)(a+b)(a-b)
=8(a+b)(a-b)²
(供参考)
(a-b)(3a+b)²+(a+3b)²(b-a)
=(a-b)(3a+b)²+-(a+3b)²(a-b)
=(a-b)[(3a+b)²-(a+3b)²]
=(a-b)(3a+b+a+3b)(3a+b-a-3b)
=(a-b)(4a+4b)(2a-2b)
=8(a-b)(a+b)(a-b)
=8(a+b)(a-b)²
(供参考)