No, is not defined at x= 0. It is thelimitof that that must be equal to b in order that the function be continuous.

Take the limit, perhaps using L'Hopital's rule, to find b.

[(e^x) - 1] / x = b

[(e^x) - 1] = (b)(x)

e^x = (b)(x) + 1

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dont know how to proceed..

should i introduce ln?