What is f(20)+f(-20) equal to?

Consider the following for the two (02) items that follow : A function f is such that f(xy)=f(x+y) for all real values of x and y, and f(5)=10.

  1. A. 0
  2. B. 10
  3. C. 20
  4. D. 40

Correct Answer: C. 20

Explanation

From the previous reasoning, f(x) = 10 for all real x. Therefore, f(20) = 10 and f(-20) = 10. The sum is 10 + 10 = 20.

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