Complex Numbers And Quadratic Equations question 619
Question: If one of the roots of equation $ x^{2}+ax+3=0 $ is 3 and one of the roots of the equation $ x^{2}+ax+b=0 $ is three times the other root, then the value of b is equal to [J & K 2005]
Options:
A) 3
B) 4
C) 2
D) 1
Show Answer
Answer:
Correct Answer: A
Solution:
Given, $ 3^{2}+a.3+3=0 $ ; $ a=-4 $ Let roots of equation $ x^{2}-4x+b=0 $ is $ \alpha $ and $ 3\alpha $ . $ \alpha +3\alpha =4 $ Þ $ 4\alpha =4 $ Þ $ \alpha =1 $ Hence $ 1-4+b=0 $ Þ $ b=3 $
BETA
