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Mathematics

If the equation 2x2 - 5x + (k + 3) = 0 has equal roots then the value of k is

  1. 98\dfrac{9}{8}

  2. 98-\dfrac{9}{8}

  3. 18\dfrac{1}{8}

  4. 18-\dfrac{1}{8}

Quadratic Equations

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Answer

Given ,

2x2 - 5x + (k + 3) = 0 has equal roots

Comparing equation with ax2 + bx + c = 0
a= 2 , b = -5 , c = k + 3

Since, equation has equal roots

∴ b2 - 4ac = 0

(5)24×2×(k+3)=0258(k+3)=0258k24=018k=08k=1k=18\Rightarrow (-5)^2 - 4 \times 2 \times (k + 3) = 0 \\[0.5em] \Rightarrow 25 - 8(k + 3) = 0 \\[0.5em] \Rightarrow 25 - 8k - 24 = 0 \\[0.5em] \Rightarrow 1 - 8k = 0 \\[0.5em] \Rightarrow 8k = 1 \\[0.5em] k = \dfrac{1}{8}

∴ Option 3 is the correct option.

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