DS - inequ

Question

guys
can you help me with this ... don´t have an OA!

cheers

scthakur · Answer

E.

From stmt1: 7x - 2y > 0, x > 0 and y can be +ve or -ve.
From stmt2, x+y > 0 and again, y can be +ve or -ve.

Combining two also gives x > 0 with y having any values.

amitdgr · Answer

can we not do the following ??

Combining the two statements .. we can solve the two inequalities as we solve simultaneous equations

eliminating x
a) 7x-2y >0 (stmt 1)
b) 7x+7y > 0 (stmt 2 * 7)

a-b => -9y > 0 or y<0

hence C

Am I doing anything wrong ?

kman · Answer

I'll pick E.

stmt 1: y can be +ve or -ve
stmt 2: Just says -x < y. y can be -5 and x can 10. Or y can be 10 and x can be 5. Insuff

scthakur · Answer

Subtracting two inequalities is not correct all the time. For example, 2 > 0 and 3 > 0 but, (2-3) < 0. However, additions is ok.

GODSPEED · Answer

My two cents, since we don't know wether y>0 or <0 so we can't do the substraction...as our friend explained using example: 2 > 0 and 3 > 0 but, (2-3) < 0.

amitdgr · Answer

Ok

I get it ..... Is adding 2 inequalities fine ?

scthakur · Answer

Addition is the only thing that should be done on inequalities. For example, a > 0, b > 0 and hence (a+b) > 0. Alternatively, a < 0, b < 0 and hence (a+b) < 0.

amitdgr · Answer

Thanks scthakur

+1

DS - inequ

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