limx→128x3+12x+1
=82limx→12x3+(12)3x+12
=4limx→12x3−(−12)3x−(−12)
Applying formula limx→axn−anx−a=nan−1
Here, n=3, a=−12
=4limx→12x3−(−12)3(−12)=4×3(−12)3−1
=4×3×14=3