If S is the sum of the first 10 terms of the series

$${\tan ^{ - 1}}\left( {{1 \over 3}} \right) + {\tan ^{ - 1}}\left( {{1 \over 7}} \right) + {\tan ^{ - 1}}\left( {{1 \over {13}}} \right) + {\tan ^{ - 1}}\left( {{1 \over {21}}} \right) + ....$$

then tan(S) is equal to :

If y = y(x) is the solution of the differential

equation $${{5 + {e^x}} \over {2 + y}}.{{dy} \over {dx}} + {e^x} = 0$$ satisfying y(0) = 1, then a value of y(log_e13) is :

The product of the roots of the
equation 9x² - 18|x| + 5 = 0 is :

Let $$\lambda \in $$ R . The system of linear equations
2x₁ - 4x₂ + $$\lambda $$x₃ = 1
x₁ - 6x₂ + x₃ = 2
$$\lambda $$x₁ - 10x₂ + 4x₃ = 3
is inconsistent for: