The roots of the equation 2x^2 - 4x + k = 0 are 1 and 2. Find the value of k.

Practice Questions

Q1
The roots of the equation 2x^2 - 4x + k = 0 are 1 and 2. Find the value of k.
  1. 2
  2. 4
  3. 6
  4. 8

Questions & Step-by-Step Solutions

The roots of the equation 2x^2 - 4x + k = 0 are 1 and 2. Find the value of k.
  • Step 1: Identify the given quadratic equation: 2x^2 - 4x + k = 0.
  • Step 2: Note that the roots of the equation are given as 1 and 2.
  • Step 3: Use Vieta's formulas, which state that for a quadratic equation ax^2 + bx + c = 0, the sum of the roots (r1 + r2) is equal to -b/a.
  • Step 4: Calculate the sum of the roots: 1 + 2 = 3.
  • Step 5: Set up the equation using Vieta's formula: 3 = -(-4)/2.
  • Step 6: Simplify the right side: -(-4) = 4, and 4/2 = 2, so we have 3 = 2, which confirms the roots are correct.
  • Step 7: Now, use the product of the roots, which is given by Vieta's formula as r1 * r2 = c/a.
  • Step 8: Calculate the product of the roots: 1 * 2 = 2.
  • Step 9: Set up the equation using Vieta's formula for the product: 2 = k/2.
  • Step 10: Solve for k by multiplying both sides by 2: k = 2 * 2 = 4.
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