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If the equation x^2 + 5kx + 16 = 0 has no real roots then (a) k > 8/5 (b) k < (–8)/5 (c) (–8)/5 < k < 8/5 (d) none of these

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Question

If the equation x2 + 5kx + 16 = 0 has no real roots then

Options

  • `k > 8/5`

  • `k < (-8)/5`

  • `(-8)/5 < k < 8/5`

  • none of these

MCQ
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Solution

`bb((-8)/5 < k < 8/5)`

Explanation:

It is given that the equation (x2 + 5kx + 16 = 0) has no real roots.  

∴ (b2 – 4ac) < 0

⇒ (5k)2 – 4 × 1 × 16 < 0 

⇒ 25k2 – 64 < 0 

⇒ `k^2 < 64/25` 

⇒ `(-8)/5 < k < 8/5`

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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 25. | Page 239
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