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Question

If limx1lnxx=ab ( where b0) and the equation ax3+x2+bx+1=0 has equal roots, then the value of |a|+|b| is

A
1
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B
2
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C
3
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D
4
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Solution

The correct option is B 2
ab=limx1lnxx =limx1lnxlnex
=limx1ln(xex)
For x, xex0
So, ln(0)
ab=0a=0

x2+bx+1=0
Equation has equal roots.
So, D=b24=0b=±2
|a|+|b|=2

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