Chapter 4 - Integration - 4.6 The Fundamental Theorem Of Calculus - Exercises Set 4.6 - Page 322: 57

(b) $x=1$ $(a)(0,+\infty)$

(a)The integration evaluation gives $F (x)=\ lnx$, which is defined only for positive values, and therefore the function represents only an antiderivative on $(0,+\infty)$ (b) The function crosses the $x$ axis if the function becomes zero. We know that $F (1)=0$.