Question

f(x)=4/x^2-cx+9
When the rational function f given by the equation above is graphed in the xy-plane, what value of c will produce exactly one vertical asymptote?
A. 0
B. 4
C. 6
D. 9

Answer 1

you get a vertical asymptote when the denominator is zero.
You get one root in a quadratic when it is a perfect square i.e. (x+a)^2
so this problem is like "completing the square" but "backwards"

Answer 2

hmm, ok, thanks!