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Rangpur Higher Secondary 2011/3

Posted: Wed Feb 02, 2011 9:05 pm
by BdMO
Problem 3:
If $-3<f<4$ and $-2<g<1$, then what is the range of possible values of $fg$?

Re: Rangpur Higher Secondary 2011/3

Posted: Wed Feb 02, 2011 11:45 pm
by leonardo shawon
its $6<fg<4$
i did this way,, i multiple the upper limit and lower limit of f and g.

Re: Rangpur Higher Secondary 2011/3

Posted: Thu Feb 03, 2011 12:08 am
by Mehfuj Zahir
THE INTERVAL OF fg should be [-8,6]

Re: Rangpur Higher Secondary 2011/3

Posted: Thu Feb 03, 2011 2:02 am
by leonardo shawon
$-3<f<1$ and $-2<g<4$
if $f=-2.90$ and $g=-1.90$ their multiple $fg$ will give a positive answer!!!
thats why $6<fg<4$

Re: Rangpur Higher Secondary 2011/3

Posted: Thu Feb 03, 2011 2:27 am
by Mehfuj Zahir
if one of them is negative then?first time i was wrong the ans is (-8,6)

Re: Rangpur Higher Secondary 2011/3

Posted: Fri Feb 04, 2011 6:05 pm
by *Mahi*
leonardo shawon wrote:$-3<f<1$ and $-2<g<4$
if $f=-2.90$ and $g=-1.90$ their multiple $fg$ will give a positive answer!!!
thats why $6<fg<4$
It's two ranges of $f$ and $g$ .It doesn't mean that if $f$ is $-3$ then $g$ is $-2$.

Re: Rangpur Higher Secondary 2011/3

Posted: Fri Feb 04, 2011 11:42 pm
by leonardo shawon
i got that later. My mistake! Sowry