What is the value of k if the quadratic equation x^2 + kx + 16 = 0 has equal roo

Practice Questions

Q1
What is the value of k if the quadratic equation x^2 + kx + 16 = 0 has equal roots?
  1. -8
  2. -4
  3. 4
  4. 8

Questions & Step-by-Step Solutions

What is the value of k if the quadratic equation x^2 + kx + 16 = 0 has equal roots?
Correct Answer: -8 or 8
  • Step 1: Identify the quadratic equation given, which is x^2 + kx + 16 = 0.
  • Step 2: Recall that for a quadratic equation ax^2 + bx + c = 0, the discriminant is given by the formula D = b^2 - 4ac.
  • Step 3: In our equation, a = 1, b = k, and c = 16.
  • Step 4: Substitute the values into the discriminant formula: D = k^2 - 4*1*16.
  • Step 5: Simplify the expression: D = k^2 - 64.
  • Step 6: For the roots to be equal, set the discriminant D to 0: k^2 - 64 = 0.
  • Step 7: Solve the equation k^2 - 64 = 0 by adding 64 to both sides: k^2 = 64.
  • Step 8: Take the square root of both sides: k = ±8.
  • Step 9: The possible values for k are 8 and -8. Since the question asks for the value of k, we can choose -8.
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