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- $\int f(x) \cdot d x=2 x+C$
- $\int f(x) d x=x^{2}+4 x+C$
- $\int f(x) \cdot d x=\frac{x^{3}}{3}+4 x+C$
- $\int f(x) \cdot d x=x^{3}+4 x+C$