Quadratic equations with complex roots

2010013201

Level: 
A
Find the complex roots of the following quadratic equation. \[ 3x^2 + 8 = 0 \]
\( x_1=-\frac{2\sqrt{6}}3\mathrm{i},\ x_2=\frac{2\sqrt{6}}3\mathrm{i} \)
\( x_1=-\frac{\sqrt{6}}3\mathrm{i},\ x_2=\frac{\sqrt{6}}3\mathrm{i} \)
\( x_1=-\frac{\sqrt{12}}3\mathrm{i},\ x_2=\frac{\sqrt{12}}3\mathrm{i} \)
\( x_1=-\frac{\sqrt{6}}6\mathrm{i},\ x_2=\frac{\sqrt{6}}6\mathrm{i} \)

2000001512

Level: 
A
Let \( x_1=2-\frac{\sqrt{5}}{2}i\) be one of the roots of a quadratic equation with real coefficients. Find the other root \(x_2\) of this equation.
\( x_2 =2+\frac{\sqrt{5}}{2}i\)
\( x_2 =-2-\frac{\sqrt{5}}{2}i\)
\( x_2 =-2+\frac{\sqrt{5}}{2}i\)
\( x_2 = \frac{1}{2-\frac{\sqrt{5}}{2}i}\)

2000001511

Level: 
B
Find the solution set of the equation \( (2x-2i)(2x+4i)(2x^2-4)=0\) in the set of complex numbers.
\( \left\{ i;-2i;\sqrt{2};-\sqrt{2} \right\}\)
\( \left\{ i;-2i \right\}\)
\( \left\{ i;-2i;\sqrt{2}i;-\sqrt{2}i \right\}\)
\( \left\{- i;2i;\sqrt{2};-\sqrt{2} \right\}\)

2000001506

Level: 
A
Factorize the equation \(4x^2+25=0\) in the set of complex numbers.
\( 4\left( x-\frac{5}{2}i\right)\left( x+\frac{5}{2}i\right)=0\)
\(( 2x+5)( 2x+5)=0\)
\( 4\left( x+\frac{5}{2}i\right)\left( x+\frac{5}{2}i\right)=0\)
\( 4\left( x-\frac{5}{2}i\right)\left( x-\frac{5}{2}i\right)=0\)

2000001505

Level: 
B
Which of the numbers below does not satisfy the equation \(2x^2=-16\)?
\( \sqrt{8}(\cos{\pi} +i\sin{\pi})\)
\( 2\sqrt{2}(\cos{\frac{\pi}{2}} +i\sin{\frac{\pi}{2}})\)
\( 2\sqrt{2}\left(\cos{\left(-\frac{\pi}{2}\right)} +i\sin{\left(-\frac{\pi}{2}\right)}\right)\)
\( 2\sqrt{2}i\)