limx→∞5x3−6x√9+4x6
=limx→∞5x3−6x√9+4x6=limx→∞x3(5−6xx3)√x6(9x6+4)
=limx→∞x3(5−6xx2)x3√9x6+4
=limx→∞5−6xx2√9x6+4
as x→∞,1x→0
=5√4=52