Limits & Continuityhard
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A pool is filled by two pipes. Pipe A rate is RA(x)=1xR_A(x) = \frac{1}{x} and Pipe B rate is RB(x)=1x+4R_B(x) = \frac{1}{x+4}. What is the limit of the combined time T(x)=1RA+RBT(x) = \frac{1}{R_A + R_B} as xx \to \infty?