(a+2b)[(a+2b)²-6ab]

(a+2b)[(a+2b)²-6ab]
(a+2b)[(a+2b)²-6ab]

(a+2b)[(a+2b)²-6ab]
原式=(a+2b)(a²+4ab+4b²-6ab)
=(a+2b)(a²-2ab+4b²)
=a³+(2b)³
=a³+8b³

(a+2b)[(a+2b)²-6ab]
=(a+2b)(a²+4ab+4b²-6ab)
=(a+2b)(a²-2ab+4b²)
=a(a²-2ab+4b²)+2b(a²-2ab+4b²)
=a³-2a²b+4ab²+2a²b-4ab²+8b³
=a³+8b³

(a+2b)＜a的平方+4ab+b的平方－6ab>
=(a+2b)（a的平方_2ab+b的平方）
=a的立方－3ab的平方+2b的立方
=