NDA Math Mock Test 03 – Question 89

Question:

The coefficient of \(x\) in the equation \(x^2 + px + q = 0\) was taken as 17 in place of 13, and its roots were found to be -2 and -15. The roots of the original equation are:

समीकरण \(x^2 + px + q = 0\) में \(x\) का गुणांक 13 के स्थान पर 17 लिया गया था, और इसके मूल -2 और -15 पाए गए। मूल समीकरण के मूल क्या हैं?

Options:

  • 3, 10
  • -3, -10
  • -5, -18
  • None of these
  • 3, 10
  • -3, -10
  • -5, -18
  • इनमें से कोई नहीं

Correct Answer: b)

Explanation:

When \(p = 17\) was used, the roots were -2 and -15.
The constant term \(q\) was recorded correctly:
\[q = \text{product of roots} = (-2) \times (-15) = 30\]
The original equation had \(p = 13\) and \(q = 30\):
\[x^2 + 13x + 30 = 0\]
Factoring the quadratic equation:
\[(x + 3)(x + 10) = 0 \implies x = -3, \; -10\]
Hence, the correct option is (b).

गलत गुणांक 17 के साथ मूल -2 और -15 थे।
अचर पद \(q = (-2)(-15) = 30\) सही था।
मूल समीकरण (जहाँ \(p = 13\)):
\[x^2 + 13x + 30 = 0 \implies (x + 3)(x + 10) = 0 \implies x = -3, -10\]
अतः सही विकल्प (b) है।

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