Question

Which of the following equation has imaginary roots?

• A. $x^2+2\sqrt{2}x+1$
• B. $x^2+4x+1=0$
• C. $3x^2+7x+9$
• D. $2x^2+5x+3=0$

Answer 1

The correct option is C

$3x^2+7x+9$

For $x^2+4x+1=0$
$△=16-4\times 1>0$
$\Rightarrow$Real Roots

For $2x^2+5x+3=0$
$△=25-4\times 2\times 3>0$
$\Rightarrow$Real Roots

For $3x^2+7x+9=0$
$△=7^2-4\times 3\times 9<0$
$\Rightarrow$Imaginary Roots

For $x^2+2\sqrt{2}x+1$
$△=(2\sqrt{2}{)}^2-4$ x $1>0$
$\Rightarrow$Real Roots