Sir thank you very much for explaining me everything so clearly.

I am getting the following conditions:

4 real distinct roots-  r  (0,3)

no real root- r > 128

only 2 real distinct roots- r  ( 3, 128 )

only 3 real roots- r = 3

only 2 real equal roots- r = 128

atleast 2 real roots- r < 128