Identify the real number \(x\)
which converts the numbers \(a_{1} = -x\),
\(a_{2} = -5\) and
\(a_{3} = 5\) into
three consecutive numbers of a geometric series.
Identify the real number \(x\)
which converts the numbers \(a_{1} = 2^{x-4}\),
\(a_{2} = 1\) and
\(a_{3} = 2^{x}\) into
three consecutive terms of a geometric series.
One of the solutions of the quadratic equation
\[
2x^{2} + px + 5 = 0
\]
with a real parameter \(p\)
is
\[
x_1 = -1 + \frac{\sqrt{6}}
{2} \mathrm{i}.
\]
Find the value of \(p\).
In the arithmetic sequence given by the first term
\(a_{1} = 4\) and the common
difference \(d = 2\)
find the sum of the first twelve terms of the sequence.