Question

Find the value of k such that lim-->4 (x^2+x-k)/(x-4) exists

Answer 1

k=20

Explanation:

when x approaches 4, the denominator x-4 approaches 0

if the denominator is 0, it means that this is invalid

if the function is a number over 0 when x=4, it represents a vertical asymptote, which means no limit

so the only way possible to let there be a limit is to let the function be 0/0 when we plug in x=4

so x^2 + x - k = 0 when x = 4

4^2 + 4 - k = 0 ==> 20 - k = 0 ==> k = 20