Multiple choice

If roots of equation ${ x }^{ 2 }+x+1=0$ are $a$, $b$ and roots of ${ x }^{ 2 }+px+q=0$ are $\dfrac { a }{ b } $, $\dfrac { b }{ a }$; then the value of $p+q$ is

  1. $2$
  2. $\dfrac { \sqrt { 2 } +1 }{ 2 } $
  3. $-1$
  4. $1$
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A Correct answer
Explanation

The roots of x^2+x+1=0 are omega and omega^2. The roots of the second equation are (a/b) and (b/a), which are (omega/omega^2) = omega^2 and (omega^2/omega) = omega. Thus, the second equation is also x^2+x+1=0, meaning p=1 and q=1. Therefore, p+q=2.

AI explanation

For the equation x^2 + x + 1 = 0, the sum of the roots a + b equals -1 and the product ab equals 1. The roots of x^2 + px + q = 0 are a/b and b/a. The sum of these new roots is a/b + b/a = (a^2 + b^2)/ab, which equals ((a + b)^2 - 2ab)/ab. Substituting the known values gives ((-1)^2 - 2)/1 = -1, so p = -1. The product of the new roots is (a/b)(b/a) = 1, so q = 1. Therefore, p + q = -1 + 1 = 2.