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Question: Answered & Verified by Expert
The value of $k$ for which $2 x^2-k x+x+8=0$ has equal and real roots are
MathematicsQuadratic EquationJEE Main
Options:
  • A -9 and -7
  • B 9 and 7
  • C -9 and 7
  • D 9 and -7
Solution:
1450 Upvotes Verified Answer
The correct answer is: 9 and -7
Equation $2 x^2-k x+x+8=0$ has equal and real roots, then $D=b^2-4 a c=0$
$\Rightarrow(1-k)^2-4.2 .8=0 \Rightarrow k^2+1-2 k-64=0$
$\Rightarrow k^2-2 k-63=0 \Rightarrow k=9,-7$

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