Question

Which of the following equations has imaginary roots?

Options

• x² + 10x – 3 = 0

• 2x² – 5x + 9 = 0

• x² + 5x + 4 = 0

• 5x² – 8x – 1 = 0

Answer 1

2x² – 5x + 9 = 0

Explanation:

For equation x² + 10x – 3 = 0;

We have a = 1; b = 10 and c = – 3

Here D = b² – 4ac

= 10² – 4 × 1 × (– 3)

= 100 + 12

= 112 > 0

∴ Roots are real.

For equation 2x² – 5x + 9 = 0;

We have, a = 2; b = – 5 and c = 9

Here D = b² – 4ac

= (– 5)² – 4 × 2 × 9

= 25 – 72

= – 47 < 0

∴ Roots are non-real or imaginary.