There are two ways that I can think of:
1) Graphing: answers = 1.0897554 and 3.9102446
2) Quadratic formula: ((7+(4*(3^(1/2))))^(t^2-5 t+5))+((7-(4*(3^(1/2))))^(t^2-5 t+5))=14
Notice that, on the left side, you have two equal terms, the equation can be reduced to:
2*((7-(4*(3^(1/2))))^(t^2-5 t+5))=14
which becomes: (7-(4*(3^(1/2)))^(t^2-5 t+5)=7
Take the log of both sides: log(7-(4*(3^(1/2)))^(t^2-5 t+5) = log(7)
---> (t^2-5 t+5) * log(7-(4*(3^(1/2))) = log(7)
---> (t^2-5 t+5) = log(7) / log(7-(4*(3^(1/2)))
---> t^2-5 t+5 = 0.9774385152
---> t^2-5 t+ (5 - 0.9774385152) = 0
---> a = 1, b = -5, c = (5 - 0.9774385152)
Placing these values into the quadratic formula gives the same results.