xyz ≠ 0 is x (y + z) >= 0

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xyz ≠ 0 is x (y + z) >= 0

by arora007 » Fri Aug 13, 2010 5:16 am
If xyz ≠ 0, is x (y + z) >= 0?

(1) ¦y + z¦ = ¦y¦ + ¦z¦
(2) ¦x + y¦ = ¦x¦ + ¦y¦

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by clock60 » Fri Aug 13, 2010 5:45 am
is xy+xz>0
(1) the 1 st is valid if
y>0,z>0
or
y<0,z<0
but we have no info about x insuff
(2) the same picture
x>0,y>0
or
x<0,y<0
z is not mentioned
both
if y>0,z>0 thus x>0 and xy+xz>0

if y<0, z<0 x<0 again xy+xz>0
C is sufficient

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by bdiwakarteja » Fri Aug 13, 2010 6:40 am
clock60 wrote:is xy+xz>0
(1) the 1 st is valid if
y>0,z>0
or
y<0,z<0
but we have no info about x insuff
(2) the same picture
x>0,y>0
or
x<0,y<0
z is not mentioned
both
if y>0,z>0 thus x>0 and xy+xz>0

if y<0, z<0 x<0 again xy+xz>0
C is sufficient
could you elaborate on this please?