The probability of selecting integers a$$\in$$[$$-$$ 5, 30] such that x² + 2(a + 4)x $$-$$ 5a + 64 > 0, for all x$$\in$$R, is :

Let the tangent to the parabola S : y² = 2x at the point P(2, 2) meet the x-axis at Q and normal at it meet the parabola S at the point R. Then the area (in sq. units) of the triangle PQR is equal to :

Let $$\overrightarrow a $$, $$\overrightarrow b $$, $$\overrightarrow c $$ be three mutually perpendicular vectors of the same magnitude and equally inclined at an angle $$\theta$$, with the vector $$\overrightarrow a $$ + $$\overrightarrow b $$ + $$\overrightarrow c $$. Then 36cos²2$$\theta$$ is equal to ___________.

Let $$A = \left( {\matrix{ 1 & { - 1} & 0 \cr 0 & 1 & { - 1} \cr 0 & 0 & 1 \cr } } \right)$$ and B = 7A²⁰ $$-$$ 20A⁷ + 2I, where I is an identity matrix of order 3 $$\times$$ 3. If B = [b_ij], then b₁₃is equal to _____________.