问题5：我们为什么要引入“多项式时间 验证”某个语言（问题）？ We define a verification algorithm as being a two-argument algorithm A,where one argument is an ordinary input string x and the other is a binary string y called a certificate.A two-argument algorithm A verifies an input string x if there exists a certificate y such that A(x,y)=1.The language verified by a verification algorithm A is L={x∈{0，l}*:there exists y∈{0，l}*such that A(x,y)=l}.问题5：我们为什么要引入“多项式时间 验证”某个语言（问题）？