Complex Numbers And Quadratic Equations question 181
Question: If the product of roots of the equation $ x^{2}-3kx+2{e^{2\log k}}-1=0 $ is 7, then its roots will real when [IIT 1984]
Options:
A) $ k=1 $
B) $ k=2 $
C) $ k=3 $
D) None of these
Show Answer
Answer:
Correct Answer: B
Solution:
Given equation can be written as $ x^{2}-3kx+2k^{2}-1=0 $ So the product of roots is $ 2k^{2}-1 $ . But the product of roots is 7. Hence $ 2k^{2}-1=7\Rightarrow 2k^{2}=8\Rightarrow k=\pm 2 $ But k cannot be negative.
BETA
