Let P(n) be true for n=m, that is, we suppose that
P(m)=2+5+8+11+...+(3m−1)= 12 m (3m + 1)
Now P(m + 1) = P(m) + Tm+1
=12m(3m+1)+[3(m+1)−1]
=12[3m2+m+6m+6−2]
=12[3m2+7m+4]
=12(m+1)(3m+4)
=12(m+1)[3(m)+1]
Above relation shows that P(n) is true for n = m + 1.
Also when n = 1,P(n) = 2 = 12(3⋅1+1)
n = 2, (P(n) = 2 + 5 = 7 = 12⋅2(3⋅2+1)
Above relation shows that P(n) is true for n = 1,2 etc.
Hence P(n) is universally true by mathematical induction.