P D * 的取值范围

D1的取值

0 P D * < 2 k + 1 ( k + 1 ) 2

k 2 + k 2 k + 2 P * ( k 2 + 2 k + 2 ) k 2 + 2 k + 2

2 k + 1 ( k + 1 ) 2 P D * < 2 k + 2 k 2 + 2 k + 2

k 2 + k ± 2 k + 2 P * ( k 2 + 2 k + 2 ) k 2 + 2 k + 2

P D * = 2 k + 2 k 2 + 2 k + 2

k 2 + k k 2 + 2 k + 2

P * > 2 k + 2 k 2 + 2 k + 2

( k + 1 ) 1 P * k 2 + 2 k + 2