limy→0 1+1+y4−2y4

Clearly,limy→0 1+1+y4−2y4=limy→0 1+1+y4−2y4×1+1+y4+21+1+y4+2 [rational isi ng the numerator]=limy→0 1+1+y4−2y41+1+y4+2∵(a+b)(a−b)=a2−b2=limy→0 1+y4−1y41+1+y4+2×1+y4+11+y4+1 [again, rational ising the numerator][by cancelling y4 and then by direct substitution]142