x\neq 0 \Rightarrow {1\over {1+x^{3}+\sqrt{1+x^{6}}}} = {{1+x^{3}-\sqrt{1+x^{6}}}\over {2\cdot x^{3}}} = {1\over 2} + {1-\sqrt{1+x^{6}}\over {2\cdot x^{3}}}