Question For Mathematicians

[ZZZZ Snoozer]

Simple question fo mathematicians

If x > 0 and y > 0

How do you formally prove x+y > 0

Add y to both sides of "x > 0"
then x + y > y and y > 0 so x + y > 0
QED

[Churchill]

So if x =9 and y=-8?

y isn't >0 in your example.

[Bagpuss]

Simple question fo mathematicians

If x > 0 and y > 0

How do you formally prove x+y > 0

ditto Churchill's answer

[BrilloPad]

y isn't >0 in your example.

exactly - so the proof was c**p

[BlasterBates]

The thing we are proving is.

x>0 y>0 implies x+y>0

y = -8 doesn't break the original proposition.

Does It?

[wendigo100]

The thing we are proving is.

x>0 y>0 implies x+y>0

y = -8 doesn't break the original proposition.

Does It?

I'm not sure I'm with you. It breaks the bit that says y>0 doesn't it?

[BlasterBates]

That's the whole point

y>0 and x>0

then x+y>0

y>0 and x>0 are preconditions for the proposition.

That means under those possibilities where x and y are both bgger than 0 then x+y is bigger than 0.

This proposition ignores y and y less then or equal to zero.

[Bagpuss]

That's the whole point

y>0 and x>0

then x+y>0

y>0 and x>0 are preconditions for the proposition.

That means under those possibilities where x and y are both bgger than 0 then x+y is bigger than 0.

This proposition ignores y and y less then or equal to zero.

So you want to prove 2 positive numbers added together are a possitive number?

[BlasterBates]

correct

[Diver]

lmnOpqrstuvwXYz

X & Y come after O in the alphabet whats the problem