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Mathematics

If the equation 3x2 - kx + 2k = 0 has equal roots, then the value(s) of k is (are)

  1. 6
  2. 0 only
  3. 24 only
  4. 0 or 24

Quadratic Equations

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Answer

Given ,

3x2 - kx + 2k = 0 has equal roots

Comparing equation with ax2 + bx + c = 0
a= 3 , b = -k , c = 2k

Since, equation has equal roots

∴ b2 - 4ac = 0

(k)24×3×2k=0k224k=0k(k24)=0k=0 or k24=0k=0 or k=24\Rightarrow (-k)^2 - 4 \times 3 \times 2k = 0 \\[0.5em] \Rightarrow k^2 - 24k = 0 \\[0.5em] \Rightarrow k(k - 24) = 0 \\[0.5em] \Rightarrow k = 0 \text{ or } k - 24 = 0 \\[0.5em] k = 0 \text{ or } k = 24 \\[0.5em]

∴ Option 4 is the correct option.

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