Question

（A+3B）的平方-（3A+B）的平方的结果是

Answer 1

(a+3b)²-(3a+b)²
=(a+3b+3a+b)(a+3b-3a-b)
=(4a+4b)(2b-2a)
=8(a+b)(b-a)

Answer 2

(a+3b)²-（3a+b)²
=(a²+6ab+9b²)_(9a²+6ab+b²)
=a²+9b²-9a²-b²
=8b²-8a²
=8(b-a)(b+a)