A) -9 and -7
B) 9 and 7
C) -9 and 7
D) 9 and -7
Correct Answer: D
Solution :
Equation \[2{{x}^{2}}-kx+x+8=0\] has equal and real roots, then\[D={{b}^{2}}-4ac=0\]. Þ \[{{(1-k)}^{2}}-4.2.8=0\]Þ \[{{k}^{2}}+1-2k-64=0\] Þ \[{{k}^{2}}-2k-63=0\]\[\Rightarrow k=9,\ -7\].
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