(a²-0,45a+1,2)+(0,8a²-1,2a)-(1,6a²-2a) =

Let's simplify the expression step by step:

1. Distribute any coefficients (in this case, they are already factored in): \[ (a^2 - 0.45a + 1.2) + (0.8a^2 - 1.2a) - (1.6a^2 - 2a) \]

2. Rewrite the expression, changing the sign of the third group: \[ a^2 - 0.45a + 1.2 + 0.8a^2 - 1.2a - 1.6a^2 + 2a \]

3. Combine like terms:

   • For \(a^2\) terms: \[ a^2 + 0.8a^2 - 1.6a^2 = (1 + 0.8 - 1.6)a^2 = 0.2a^2 \]
   • For \(a\) terms: \[ -0.45a - 1.2a + 2a = (-0.45 - 1.2 + 2)a = (2 - 1.65)a = 0.35a \]
   • Constant term: \[ 1.2 \]

4. Combine all the simplified parts: \[ 0.2a^2 + 0.35a + 1.2 \]

So the final simplified expression is: \[ \boxed{0.2a^2 + 0.35a + 1.2} \]