# Do you know your functions?

Algebra Level 4

The following functions are defined as $$f(x) : \mathbb{R} \rightarrow \mathbb{R}$$

Which of these functions are bijective?

$$1.f(x) = x^2 + 2x - 1$$

$$2.f(x) = \log(x) + |x|$$

$$3. f(x)=\log(x)$$

$$4. f(x)= x^2$$

$$5. f(x)=2^x$$

Assume $$\log(x)$$ indicates the natural logarithm function.

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