limx→∞{3x2+14x2−1}x31+x
limx→∞{3x2+14x2−1}x31+x=limx→∞{1+−x2+24x2−1}x31+x=elimx→∞{(−x2+24x2−1)(x31+x)}=elimx→∞{(−x5+2x34x2−1+4x3−x)}=e−∞=0
limx→∞x√4x2+1−1