Given that \(\frac{1}{x^2 - 4} = \frac{p}{(x + 2)} + \frac{Q}{(x - 2})\)

x \(\neq \pm 2\)

Find the value of (P + Q)

Find the sum of the first 20 terms of the sequence -7-3, 1, ......

Find the value of x for which 6\(\sqrt{4x^2 + 1}\) = 13x, where x > 0

Calculate the distance between points (-2, -5) and (-1, 3) 

If P = \(\begin {pmatrix} 2 & 3\\  -4 & 1 \end {pmatrix}\), Q = \(\begin{pmatrix} 6 \\ 8 \end {pmatrix}\) and PQ = k \(\begin {pmatrix} 45\\ -20 \end {pmatrix}\). Find the value of k.