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Sticky Note
If x² + kx + 4 = 0 has roots differing by 2, then k equals?
  1. -2√5
  2. 2√5
  3. Both A and B
  4. None of these
Explanation

Let roots be r and r+2, since they differ by 2.

For x² + kx + 4 = 0:

1. Sum of roots = -b/a = -k → r + (r+2) = 2r + 2 = -k → r = (-k-2)/2

2. Product of roots = c/a = 4 → r(r+2) = 4

Plug r in: [(-k-2)/2] × [(-k-2)/2 + 2] = 4  

→ [(-k-2)/2] × [(2-k)/2] = 4  

→ (-k-2)(2-k) = 16

Simplify: k² - 4 = 16 → k² = 20 → k = ±2√5

So k can be 2√5 or -2√5.


Last verified 09-06-2026

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