How do you find intercepts, extrema, points of inflections, asymptotes and graph f(x)=x/sqrt(x^2+7)?

1 Answer
May 7, 2018

See below.

Explanation:

Both intercepts are 0.

sqrt(x^2+7) > 0 for all x, so there are no vertical asymptotes.

lim_(xrarroo)f(x) = lim_(xrarroo)x/(xsqrt(1+7/x^2)) = 1, so y=1 is a horizontal asymptote on the right.

lim_(xrarr-oo)f(x) = lim_(xrarr-oo)x/(-xsqrt(1+7/x^2)) = -1, so y = -1 is a horizontal asymptote on the left.

f'(x) = 7/(x^2+7)^(3/2) > 0 for all x, so there are no local extrema.

f''(x) = (-21x)/(x^2+7)^(5/2) changes sign at (0,0), so I have been taught that (0,0) is an inflection point. (Note that: f'(0) != 0, so some would say (0,0) is not an inflection point.)

graph{x/sqrt(x^2+7) [-16.01, 16.03, -7.95, 8.05]}