4. Let f:R->R be a function with Taylor series converging to f(x) for all real numbers x. If f(0) = 2, f’(0) = 2, and f(n)(0) = 3 for n >= 2, then f(x) =

A. 3ex + 2x - 1

B. e3x + 2x + 1

C. e3x - x + 1

D. 3ex - x - 1

E. 3ex + 5x + 5

 

Solution: The answer is D

 

Since f(x) has a Taylor series converging to f(x) for all real numbers x, consider the Taylor series of f(x) centered at 0, such that,

Substituting the given values, f(0) = 2, f’(0) = 2, and f(n)(0) = 3 for n >= 2, into the above equation yields:

Since,

Thus,