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Mathematics

If the quadratic equation, px2 - 252\sqrt{5} px + 15 = 0 has two equal roots, then the value of p is:

  1. 0

  2. 3

  3. 6

  4. both 0 and 3

Quadratic Equations

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Answer

Comparing px2 - 252\sqrt{5} px + 15 = 0 with ax2 + bx + c = 0 we get,

a = p, b = 25-2\sqrt{5} p and c = 15.

We know that,

Since equations has equal roots,

⇒ D = 0

⇒ b2 - 4ac = 0

⇒ (25-2\sqrt{5} p)2 - 4(p)(15) = 0

⇒ 20p2 - 60p = 0

⇒ 20p(p - 3) = 0

⇒ 20p = 0 or (p - 3) = 0      [Using Zero-product rule]

⇒ p = 0 or p = 3.

Since p = 0 would make the equation no longer quadratic, we take:

p = 3

Hence, option 2 is the correct option.

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