①(x-2y)²乘(x+2y)²②（a-3)²—（a+3）²以上题能用简便方法用简便方法,

①(x-2y)²乘(x+2y)²②（a-3)²—（a+3）²以上题能用简便方法用简便方法,
①(x-2y)²乘(x+2y)²②（a-3)²—（a+3）²以上题能用简便方法用简便方法,

①(x-2y)²乘(x+2y)²②（a-3)²—（a+3）²以上题能用简便方法用简便方法,
①(x-2y)²乘(x+2y)²
=[(X-2Y)(X+2Y)]²
=(X²-4Y²)²
=X^4-8X²Y²+16Y^4
②（a-3)²—（a+3）²
=[(a-3)+(a+3)][(a-3)-(a+3)]
=2a×(-6)
=-12a