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Mathematics 11 Online
OpenStudy (anonymous):

IS this quantified formulae true over the NATURAL NUMBERS (1,2,3,...) for all x there exist a y for all z there exist a w [xy = w + z]

ganeshie8 (ganeshie8):

consider x=1, y=1

OpenStudy (zarkon):

why would we consider that?

OpenStudy (anonymous):

Ah ok because if x and y are both 1 their product will be equal to 1 and w+z will always be greater than one since they can only be natural numbers (1,2,3,...) thank you

OpenStudy (zarkon):

it doesn't say for all x and all y ..it says for all x there exists a y

OpenStudy (anonymous):

hm... yeah you're right

OpenStudy (zarkon):

if you pick any x or z I can show there exists y and w such that the equation holds

OpenStudy (zarkon):

do it this way....pick any x and z then choose y to be a number such that x*y>z then choose w to be x*y-z

OpenStudy (zarkon):

then the equation holds

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