- The function is \( f(x) = x^3 + 5 \).
- To check injectivity, assume \( f(a) = f(b) \) for some \( a, b \in \mathbb{R} \).
- Then, \( a^3 + 5 = b^3 + 5 \implies a^3 = b^3 \).
- Since the cube function \( x^3 \) is strictly increasing and one-to-one on
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