19: The conditions give (in the same order):

• This condition is already solved.
• This condition is best solved by substitution y = ln(x), leading to a quadratic equation with roots y = −1 and y = 2. The inequalities ln(x) ≠ −1 and ln(x) ≠ 2 give x ≠ e⁻¹ and x ≠ e².

Now intersect these conditions.

Answer