Sketch synthesis: domain, intercepts, asymptotes, monotonicity, and concavity
Consider the function , defined for all real numbers.
The function has domain all real numbers and no vertical asymptotes. Using and , determine the complete behavior of needed for a full curve sketch: the - and -intercepts, whether is increasing or decreasing on its domain, and the coordinates of any inflection point. State the inflection point's coordinates as your final answer.
Hint
Find where and for intercepts. Check the sign of on its domain (note is undefined at but itself is still defined there, so there's no vertical asymptote). Then check where changes sign — that's the candidate inflection point, and confirm is defined and continuous there.
Step-by-step solution
Setting gives , so ; thus the -intercept is . Evaluating at gives , so the -intercept is . Since is positive for all (a square root of a real number under the cube gives a nonnegative denominator), is increasing on the entire real line, with a vertical tangent (not asymptote) at since is defined and finite.
For concavity, . For , , making (concave up); for , , making (concave down). Since concavity switches sign across and is defined, the point is an inflection point — matching the same location as the -intercept.
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