If the 10^th term of an A.P. is $${1 \over {20}}$$ and its 20^th term is $${1 \over {10}}$$, then the sum of its first 200 terms is

Let ƒ : (1, 3) $$ \to $$ R be a function defined by
$$f(x) = {{x\left[ x \right]} \over {1 + {x^2}}}$$ , where [x] denotes the greatest integer $$ \le $$ x. Then the range of ƒ is

If $$\alpha $$ and $$\beta $$ be the coefficients of x⁴ and x² respectively in the expansion of
$${\left( {x + \sqrt {{x^2} - 1} } \right)^6} + {\left( {x - \sqrt {{x^2} - 1} } \right)^6}$$, then

The system of linear equations
$$\lambda $$x + 2y + 2z = 5
2$$\lambda $$x + 3y + 5z = 8
4x + $$\lambda $$y + 6z = 10 has