Complex Numbers And Quadratic Equations question 781
Question: The expression $ x^{2}+2bx+c $ has the positive value if [Roorkee 1995]
Options:
A) $ b^{2}-4c>0 $
B) $ b^{2}-4c<0 $
C) $ c^{2}<b $
D) $ b^{2}<c $
Show Answer
Answer:
Correct Answer: D
Solution:
$ x^{2}+2bx+c={{(x+b)}^{2}}+c-b^{2} $ $ \because $ $ {{(x+b)}^{2}} $ is a perfect square, therefore the given expression is positive if $ c-b^{2}>0 $ or $ b^{2}<c $ .
BETA
