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Pawan Dubey

· started a discussion

· 1 Months ago

Question and explanation different (Question: 273458.0 )

You are asking for the condition for the root to be POSITIVE but using the CONDITION OF REAL ROOTS i.e. D>=0 ....Instead the solution should have been
Sum of roots >0 i.e. 2(K-1)>0 (from coefficients) hence K>1 and from
Product of Roots>0 2K+1>0 i.e. K>(-1/2) from these two conditions the least possible value of K is 1 for Positive Roots

Question:

For what minimum of k, x2 – 2(k – 1)x + (2k + 1) = 0 has positive roots.

Options:
A)

1

B)

-12    

C)

4

D)

0

Solution:

Ans: (c)

 

Praveen Dubey

· commented

· 1 Months ago

1 gives imaginary roots

Vijay Sharma

· commented

· 1 Months ago

agree bro... 1 should be the answer...

ROHIT KUMAR

· commented

· 1 Months ago

roots will be positive if sqrt(b^2-4ac)>b
i.e. b^2-4ac>b^2 so -4ac>0 or ac<0
Here a=1, c= (2k+1)
so 1(2k+1)<0
k<-1/2
This is minimum value of k.
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