Harsha Bhai ,harshavardhanc wrote: rocky,
we should not subtract the inequalities. Addition is okay if the inequalities have the same sign.
see this :
1) 3 > 0
2) 7 > 0
will (1) - (2) be greater than 0? no.
we can tell that (2) - (1) > 0 BECAUSE we know that 7>3.
But in the inequality, like one above, we are not sure which one is greater because of the variables. Hence, subtraction should not be done.
HTH.
What you said makes sense .
I apologies to you all as I made a silly mistake again
. We can subtract inequalities provided what you do to one side of the inequality you do the same to the other side also .This is where I made the mistake .
Here is some official explanation form MGAMT Maths Guide.
So going by this method we can not eliminate variable 'x ' in the above example and thus we can never be sure of the sign of variable 'y' .You can add or subtract a variable expression on both sides .
Ex :
y + x < 5
-y - y
----------------------
x < 5 - y
another example .
x - ab < 9
+ ab + ab
---------------------
x < 9 + ab
My sincere apologies for misguiding you all .
