Step 1: Understanding the Concept:
For continuity at $x = 1$, the left-hand limit, right-hand limit, and function value must all be equal.
Step 2: Detailed Explanation:
$f(1) = 1 + 1 = 2$.
RHL $= \lim_{x\to1^+}(3-ax^2) = 3-a$.
Continuity: $3 - a = 2 \Rightarrow a = 1$.
Step 3: Final Answer:
$a = 1$.