Quadratic equations with complex roots

9000064508

Level: 
A
Solve the following quadratic equation in the complex plane. \[ 2x^{2} + x + 1 = 0 \]
\(x_{1, 2} = \frac{-1\pm \mathrm{i}\sqrt{7}} {4} \)
\(x_{1, 2} = \frac{-1\pm \mathrm{i}\sqrt{7}} {2} \)
\(x_{1, 2} = \frac{1\pm \mathrm{i}\sqrt{7}} {4} \)
\(x_{1, 2} = \frac{1\pm \mathrm{i}\sqrt{7}} {2} \)

9000064506

Level: 
A
Find the factorization of the following quadratic polynomial in the set of polynomial with complex valued coefficients. \[ 2x^{2} + 4x + 5 \]
\(2\! \left (x + 1 + \frac{\sqrt{6}} {2} \mathrm{i}\right )\! \! \left (x + 1 -\frac{\sqrt{6}} {2} \mathrm{i}\right )\)
\(2\! \left (x - 1 + \frac{\sqrt{6}} {2} \mathrm{i}\right )\! \! \left (x - 1 -\frac{\sqrt{6}} {2} \mathrm{i}\right )\)
\(\left (x + 1 -\frac{\sqrt{6}} {2} \mathrm{i}\right )\! \! \left (x + 1 + \frac{\sqrt{6}} {2} \mathrm{i}\right )\)
\(\left (x - 1 -\frac{\sqrt{6}} {2} \mathrm{i}\right )\! \! \left (x - 1 + \frac{\sqrt{6}} {2} \mathrm{i}\right )\)

9000064503

Level: 
B
Find the values of the real coefficients \(a\), \(b\) and \(c\) such that the quadratic equation \[ ax^{2} + bx + c = 0 \] has solution \(x_{1, 2} =\pm \mathrm{i}\frac{\sqrt{5}} {3} \).
\(a = 9\text{, }b = 0\text{, }c = 5\)
\(a = 5\text{, }b = 0\text{, }c = 9\)
\(a = 9\text{, }b = 0\text{, }c = -5\)
\(a = 5\text{, }b = 0\text{, }c = -9\)