Theory of Equations 1 Question 2

2. Let p,qR. If 23 is a root of the quadratic equation, x2+px+q=0, then

(2019 Main, 9 April I)

(a) q24p16=0

(b) p24q12=0

(c) p24q+12=0

(d) q2+4p+14=0

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Answer:

Correct Answer: 2. (b)

Solution:

  1. Given quadratic equation is x2+px+q=0, where p,qR having one root 23, then other root is 2+3 (conjugate of 23 ) [ irrational roots of a quadratic equation always occurs in pairs]

So, sum of roots =p=4p=4

and product of roots =q=43q=1

Now, from options p24q12=16412=0



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