Problem

Suppose that

a

and

b

(

b \neq a

) are real positive numbers, the value of

\lim_{t \to 0} \left( \frac{b^{t+1} - a^{t+1}}{b-a} \right)

has the value equal to a. \frac{a \ln b - b \ln a}{b-a} b. \frac{b \ln b - a \ln a}{b-a} c. b \ln b - a \ln a d. \left( \frac{b^a}{a^b} \right)^{b-a}