Integrals of Exponential Functions

Key Questions

  • By rewriting a bit,

    int n^x dx=int e^{(lnn)x}dx=e^{(lnn)x}/{lnn}+C=n^x/{lnn}+C

    I hope that this was helpful.

  • The answer is I=-e^(-x)+C.

    This integral can be solved by a substitution:

    u=-x
    du=-dx
    -du=dx

    So, now we can substitute:

    int e^(-x)dx = int e^u (-du)
    =-int e^u du
    =-e^u + C

    and substitute back:
    =-e^(-x) + C

    For simple looking integrands, you should try a quick check to see if substitution works before trying harder integration methods.

  • Answer:

    int3^xdx=1/ln3 3^x+"c"

    Explanation:

    We want to find int3^xdx.

    Make the natural substitution u=3^x so du=3^xln3dx.

    So

    int3^xdx=1/ln3int1du=1/ln3 u+"c"=1/ln3 3^x+"c"

  • Since

    (e^x)'=e^x,

    we have

    int e^x dx=e^x+C.

    I hope that this was helpful.

Questions