If $\lim \limits_{x \to 0} \bigg(\large\frac{\cos 4x+a \cos 2x+b}{x^4}\bigg)$ is finite, then the values of a,b are respectively :

$\begin {array} {1 1} (a)\;5,-4 & \quad (b)\;-5,-4 \\ (c)\;-4,3 & \quad (d)\;4,5 \end {array}$

(c) -4,3
answered Nov 7, 2013 by