There exists a matrix Q such that PQP T = N, where P = [(1,2,0)(2,1,0)(0,0,1)] .
Given N is a diagonal matrix of form N = diag.(n1 , n2 , n3) where n1 , n2 , n3 are three values of n satisfying the equation det.(P - nI) = 0, n1< n2< n3 .
[Note : I is an identity matrix of order 3×3]
If QT = Q + αI, then the value of α is equal to