先化简,再求值：（a+2)(a-2)+2(a的平方+3),其中a=1/3.已知A=2x+y,B=2x-y,计算A的平方-B的平方.

1.
(a+2)(a-2)+2(a²+3)
=a²-4+2a²+6 根据公式：(a+b)(a-b)=a²-b²
=3a²+2
带入a=1/3,得：
(a+2)(a-2)+2(a²+3)
=3a²+2
=3×（1/9）+2
=7/3
2.
A²-B²
=(A+B)(A-B)
=(2x+y+2x-y)(2x+y-2x+y)
=4x*2y
=8xy