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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
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Solution
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.
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