Injective Surjective A78Fbd
1. **Problem statement:** We have a function $f: \mathbb{R} \to \mathbb{R}$ defined by $f(x) = x + 1$. We need to check if $f$ is injective, surjective, or bijective.
2. **Definitions:**
- A function is **injective** (one-to-one) if different inputs map to different outputs.
- A function is **surjective** (onto) if every element in the codomain has a preimage in the domain.
- A function is **bijective** if it is both injective and surjective.
3. **Check injectivity:**
Assume $f(a) = f(b)$ for some $a,b \in \mathbb{R}$.
$$a + 1 = b + 1$$
Subtract 1 from both sides:
$$a = b$$
Since $a = b$ whenever $f(a) = f(b)$, the function is injective.
4. **Check surjectivity:**
For any $y \in \mathbb{R}$, we want to find $x \in \mathbb{R}$ such that:
$$f(x) = y$$
Substitute $f(x) = x + 1$:
$$x + 1 = y$$
Solve for $x$:
$$x = y - 1$$
Since $x = y - 1$ is always a real number for any real $y$, every $y$ in the codomain has a preimage. Thus, $f$ is surjective.
5. **Conclusion:**
Since $f$ is both injective and surjective, it is bijective.
**Final answer:** The function $f(x) = x + 1$ is injective, surjective, and therefore bijective.