Integral of $$$4 e^{x}$$$

Apply the constant multiple rule $$$\int c f{\left(x \right)}\, dx = c \int f{\left(x \right)}\, dx$$$ with $$$c=4$$$ and $$$f{\left(x \right)} = e^{x}$$$:

$${\color{red}{\int{4 e^{x} d x}}} = {\color{red}{\left(4 \int{e^{x} d x}\right)}}$$

The integral of the exponential function is $$$\int{e^{x} d x} = e^{x}$$$:

$$4 {\color{red}{\int{e^{x} d x}}} = 4 {\color{red}{e^{x}}}$$

Therefore,

$$\int{4 e^{x} d x} = 4 e^{x}$$

Add the constant of integration:

$$\int{4 e^{x} d x} = 4 e^{x}+C$$

Answer: $$$\int{4 e^{x} d x}=4 e^{x}+C$$$