=3^(4n+4)÷3^(3n)÷3^(2n-2)×3^(n-4)
=3^(4n+4-3n-2n+2+n-4)
=3²
=9
2.[（a-b）²+4ab]÷（a+b）²
=(a²+2ab+b²)÷(a+b)²
=1