(1)∵1×3+1=4=22;2×4+1=9=32;3×5+1=16=42;4×6+1=25=52,…
∴6×8+1=72,
故答案为:7;
(2)根据已知中数据的变化规律得出:n(n+2)+1=(n+1)2;
故答案为:n(n+2)+1=(n+1)2;
(3)原式=[1×3+1/1×3×
2×4+1
2×4×
3×5+1
3×5×
4×6+1
4×6×…×
11×12+1
11×13]
=
22
1×3×
32
2×4×
42
3×5×
52
4×6×…×
122
11×13
=2×[12/13]
=[24/13].