Let $$f(x) = {{x - 1} \over {x + 1}},\,x \in R - \{ 0, - 1,1\} $$. If $${f^{n + 1}}(x) = f({f^n}(x))$$ for all n $$\in$$ N, then $${f^6}(6) + {f^7}(7)$$ is equal to :
- A$${7 \over 6}$$
- B$$ - {3 \over 2}$$
- C$${7 \over {12}}$$
- D$$ - {{11} \over {12}}$$
✓ Correct answer: B
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