Multiple choice

If the equations $\displaystyle x^{2}+3x+2=0$ and $\displaystyle x^{2}+kx+6=0$ have a common root then find the values of k

  1. $-1, -2$
  2. $5, 7$
  3. $7, -2$
  4. $-1, 5$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

If they have a common root x, then x^2+3x+2 = 0 => (x+1)(x+2)=0, so x = -1 or x = -2. If x = -1, 1 - k + 6 = 0 => k = 7. If x = -2, 4 - 2k + 6 = 0 => 2k = 10 => k = 5. Values are 5, 7.

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