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GATE 2025 AG – Question 11

Engineering Mathematics · Linear Algebra · 1 mark · Multiple choice

If a, b, c are the roots of $2x^3-3x^2+px-1=0$ and two roots sum to 1,find p.

  1. 2
  2. 1
  3. 3
  4. 1/3

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Correct answer: (C) 3

Explanation

Vieta gives $a+b+c=3/2$. Let $a+b=1$; then $c=1/2$. Also $abc=1/2$,so $ab=1$. The pairwise product sum is $ab+c(a+b)=1+1/2=3/2=p/2$. Hence **p=3,C**. The algebra permits complex roots; no assumption of three real roots is needed.

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