Question

I've gotten stuck on this problem: "Let f(z) be the branch to z13+z14, which is defined on the entire complex plane except on the negative imaginary axis, for which f(1)=0. Find f(-1)."
I started by writing z13+z14 as e13(ln|z|+iθ(z)+i2nπ)+e14(ln|z|+iθ(z)+i2mπ) but when I try to solve f(1)=0 I just get the relationship between n and m, which means I won't get a specific branch. I am also not sure how to use the condition "not defined on the negative imaginary axis"

Answer 1

In order to find the value of f(-1), you can start by finding the value of f(1) and then proceed for the next step.

As you have already noted, writing z13+z14 as e13(ln|z|+iθ(z)+i2nπ)+e14(ln|z|+iθ(z)+i2mπ) will not give you a specific branch. Instead, you can write z13+z14 as follows:

(z-1)(z12+z11+z10+...+1)

Then, you can use the fact that f(1)=0 to solve for the value of z12+z11+z10+...+1. This will give you a specific value for f(1).

To find the value of f(-1), you can use the following relationship:

f(-1) = f(1) * (-1)13 * (-1)14

Substituting the value you found for f(1) and evaluating the expression will give you the value of f(-1).

As for the condition "not defined on the negative imaginary axis", this means that the branch of f(z) is not defined for any complex number with a negative imaginary part. This is because the 13th and 14th roots of a complex number are not unique when the imaginary part is negative, so the function is not defined for these values.

Learn more about Imaginary axis at:

brainly.com/question/1142831

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