Solve[2 t^2 - 4.6 t + 1.2 - (1 - 4 t) (0.3 t - 1) == 3.2 t^2]

{{t -> -4.0082*10^16}, {t -> 0.247191}}

Solve[FullSimplify[2 t^2 - 4.6 t + 1.2 - (1 - 4 t) (0.3 t - 1)] == 3.2 t^2]

{t -> 0.247191}}

a = 2 t^2 - 4.6 t + 1.2 - (1 - 4 t) (0.3 t - 1) /.
   t -> -4.008203668359741`*^16;
b = 3.2 t^2 /. t -> -4.008203668359741`*^16;
a == b
(a - b)/a < $MachineEpsilon

2 t^2 - 4.6 t + 1.2 - (1 - 4 t) (0.3 t - 1) - 3.2 t^2 // Expand