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For what value of k, the equation kx^2 – 6x – 2 = 0 has real roots? (a) k ≤ (–9)/2 (b) k ≥ (–9)/2 (c) k ≤ –2 (d) None of these

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Question

For what value of k, the equation kx2 – 6x – 2 = 0 has real roots?

Options

  • `k ≤ (-9)/2`

  • `k ≥ (-9)/2`

  • k ≤ –2

  • None of these

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Solution

`bb(k ≥ (-9)/2)`

Explanation:

It is given that the roots of the equation (kx2 – 6x – 2 = 0) are real 

∴ D ≥ 0 

⇒ (b2 – 4ac) ≥ 0 

⇒ (–6)2 – 4 × k × (–2) ≥ 0 

⇒ 36 + 8k ≥ 0 

⇒ `k ≥ (-36)/8` 

⇒ `k ≥ (-9)/2` 

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Chapter 4: Quadratic Equations - TEST YOURSELF [Page 239]

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R.S. Aggarwal Mathematics [English] Class 10
Chapter 4 Quadratic Equations
TEST YOURSELF | Q 27. | Page 239
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