We have,
limx→∞√x2+cx−x
On rationalising numerator, we get
=limx→∞(√x2+cx−x)(√x2+cx+x)(√x2+cx+x)
=limx→∞x2+cx−x2(√x2+cx+x)
=limx→∞cx(√x2+cx+x)
=limx→∞cx(x√1+cx+x)
=limx→∞c(√1+cx+1)
When x→∞, then 1x→0
=limx→∞c(√1+c(0)+1)
=c2
Therefore,
limx→∞√x2+cx−x=c2