Q.

limx0e-(1+2x)12xx is equal to                    [2024]

1 e  
2 0  
3 -2e  
4 e-e2  

Ans.

(1)

Let L=limx0e-(1+2x)1/2xx

=limx0e-e12xlog(1+2x)x

=limx0-e(elog(1+2x)2x-1-1)x

=limx0-e[elog(1+2x)-2x2x-1]x×log(1+2x)-2x2x×log(1+2x)-2x2x

=limx0-exlog(1+2x)-2x2x                  [∵ limx0ex-1x=1]

=limx0-e[11+2x·2-24x]      [Using L'Hospital Rule]

=limx0-e4-1(1+2x)2·4             [Again by L'Hospital]

=e