MCQ
$\sum {{1 \over {1 + {x^{a - b}} + {x^{a - c}}}} = } $
  • $1$
  • B
    $-1$
  • C
    $0$
  • D
    None of these

Answer

Correct option: A.
$1$
a
(a)  $\sum\limits_{}^{} {{1 \over {1 + {x^{a - b}} + {x^{a - c}}}} = \sum\limits_{}^{} {{{{x^{b + c}}} \over {{x^{b + c}} + {x^{c + a}} + {x^{a + b}}}}} } $

= ${1 \over {{x^{b + c}} + {x^{c + a}} + {x^{a + b}}}}\sum\limits_{}^{} {{x^{b + c}}} $

= ${1 \over {{x^{b + c}} + {x^{c + a}} + {x^{a + b}}}}\,({x^{b + c}} + {x^{c + a}} + {x^{a + b}}) = 1$.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free