Im confuse about a limit question

Apr 2008
80
2
Given that lim x->c f(x)=6 and that lim x->c g(x)= -4, evaluate the following limit. Assume that c is a constant. The x in front of the f is confusing me.
lim [xf(x) + 3 g(x)]^2
x->c
 
Apr 2010
41
15
India
\(\displaystyle \lim_{x\rightarrow{c}}(xf(x)+3g(x))^2=\lim_{x\rightarrow{c}}[x^2f^2(x)+9g^2(x)+6xf(x)g(x)]
=c^2(6)^2+9(-4)^2+6c(6)(-4)\)
\(\displaystyle =36c^2+144-144c\)