Worked solution
Carry the logarithm domain through a hence inequality
Sketch . By sketching another suitable graph, solve .
Hence solve .
CJC · Lecture · Example 11
Sketch the hyperbola and add a modulus graph
Divide the inequality by the positive constant 2 to get . Sketch y=2/(x+1), with vertical asymptote x=−1 and horizontal asymptote y=0, and add y=|x|. The crossing input is x=1. Read where the hyperbola is on or below the V: x<−1 or x≥1. The pole −1 is excluded; the crossing 1 is included.
Substitute the entire logarithmic input
Divide by 2. It has the same form with the old input replaced by ln x, including inside the modulus. Thus ln x<−1 or ln x≥1.
Keep the lower domain bound and distinguish the endpoints
The logarithm requires x>0, and its denominator excludes ln x=−1. Since ln is increasing, the intervals become or . The lower interval must begin at 0, not at−∞; the source’s common-mistake note warns that this bound is often missed. The threshold e⁻¹ is excluded and e is included.
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Common mistakes
Writing only x<e⁻¹ admits nonpositive inputs where ln x is undefined. Keep the modulus bars in the substituted problem.