Complex Numbers And Quadratic Equations question 769
Question: The value of $ k $ for which $ 2x^{2}-kx+x+8=0 $ has equal and real roots are [BIT Ranchi 1990]
Options:
A) -9 and -7
B) 9 and 7
C) -9 and 7
D) 9 and -7
Show Answer
Answer:
Correct Answer: D
Solution:
Equation $ 2x^{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 $ .
BETA
