How do you sketch the curve of f(x) = (2x-3) / (2 x -9)^2?

1 Answer
Sep 11, 2015

See explanation section.

Explanation:

f(x) = (2x-3) / (2 x -9)^2

Domain: RR " - " {9/2}

x-intercept: 3/2
y intercept -1/27

Symmetry: None

Vertical Asymptote: x = 9/2
Horizontal Asymptote: y = 0 (a.k.a. the x-axis)

f'(x) = (-2(2x+3))/(2x-9)^3

Sign analysis of f' shows that:
f is decreasing on (-oo, -3/2) and on (9/2, oo) and
f is increasing on (-3/2, 9/2)

Local Minimum -1/24 (at x=-3/2)

f''(x) = (8(2x+9))/(2x-9)^4
Sign analysis of f'' shows that:
f is concave down on (-oo, -9/2) and
f is concave up on (-9/2, 9/2) and on (9/2, oo)

(-9/2, -1/27) is the only inflection point.

The graph looks like this:

graph{y=(2x-3) / (2 x -9)^2 [-6.16, 11.62, -2.91, 5.985]}

(You can scroll in and out using a mouse wheel and also drag the graph around to see features more clearly.)