a=3,b=4,c=5,
根据双曲线的定义可知,
|AF2|-|AF1|=2a,|AF2|=|AF1|+2a,
|BF2|-|BF1|=2a,|BF2|=|BF1|+2a,
|AF2|+|AF1|=2a+2|AF1|,
|BF2|+|BF1|=2a+2|BF1|,
|AB|=|AF1|+|BF1|,
△ABF2周长=|AF2|+|BF2|+|AB|
=2a+2|AF1|+2a+2|BF1|+|AB|
=4a+2*(|AF1|+|BF1|)+|AB|
=3*4+2*12+12
=48.
a=3,b=4,c=5,
根据双曲线的定义可知,
|AF2|-|AF1|=2a,|AF2|=|AF1|+2a,
|BF2|-|BF1|=2a,|BF2|=|BF1|+2a,
|AF2|+|AF1|=2a+2|AF1|,
|BF2|+|BF1|=2a+2|BF1|,
|AB|=|AF1|+|BF1|,
△ABF2周长=|AF2|+|BF2|+|AB|
=2a+2|AF1|+2a+2|BF1|+|AB|
=4a+2*(|AF1|+|BF1|)+|AB|
=3*4+2*12+12
=48.