Let f: R → R satisfy f(x + y) = f(x) + f(y) for all x, y in R. If f(1) = 7, then the value of f(4) is:
Let f: R → R satisfy f(x + y) = f(x) + f(y) for all x, y in R. If f(1) = 7, then the value of f(4) is:
- A. 11
- B. 28
- C. 49
- D. 7
Answer: B) 28
Explanation: Using the functional equation f(x+y) = f(x)+f(y), we get f(nx) = n f(x) for integer n. So, f(4) = 4 × f(1) = 4 × 7 = 28.
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