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Mathematics

The value(s) of k for which the quadratic equation 2x2 - kx + k = 0 has equal roots is (are)

  1. 0 only
  2. 4
  3. 8 only
  4. 0, 8

Quadratic Equations

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Answer

Given ,

2x2 - kx + k = 0 has equal roots

Comparing equation with ax2 + bx + c = 0
a= 2 , b = -k , c = k

Since, equation has equal roots

∴ b2 - 4ac = 0

(k)24×2×k=0k28k=0k(k8)=0k=0 or k8=0k=0 or k=8\Rightarrow (-k)^2 - 4 \times 2 \times k = 0 \\[0.5em] \Rightarrow k^2 - 8k = 0 \\[0.5em] \Rightarrow k(k - 8) = 0 \\[0.5em] \Rightarrow k = 0 \text{ or } k - 8 = 0 \\[0.5em] k = 0 \text{ or } k = 8 \\[0.5em]

∴ Option 4 is the correct option.

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