xz>0 implies either x and z are both positive or both negative.diebeatsthegmat wrote: sorry i dont understand the xz part
from the info we know y^2>0 with all y,
xz>0 so z,x must be both + or both (-)
if x<0 and z<0 z^3*x^7>0 so x^7*y^2*z^3>0 ( yes)
if x>0 and y>0 of course x^7y^2z^3>0
so i think this condition is sufficient....
why is it not/???? i dont get it, please give me a fast explanation
If x and z are positive then (x^7)(y^2)(z^3) > 0.
If x and z are negative then (x^7)(y^2)(z^3) > 0.
But nothing is given about y, if y = 0, then (x^7)(y^2)(z^3) = 0
No unique answer.
So, (1) is NOT SUFFICIENT. Does that help?
