How to solve UNLESS statements AND contrapositives with ease

[celphi02]

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UNLESS STATEMENTS
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OK so here's an easy way to solve UNLESS statements.

If apples then oranges.

A --> O

IF on this side --> THEN on this side (remember this format)

If not apples then not oranges

~A --> ~O

Again IF portion on left side (of --> sign) and THEN on right side.

You must understand the above 1st before going on.

UNLESS statements is the same as saying IF NOT.

So.,

No apples unless oranges.
Read it as: IF NOT oranges then NO apples.

~O --> ~A

I found this way to solve all my UNLESS statements with a breeze.


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CONTRAPOSITIVES
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If the contra-positive part is confusing you then do the following.

Example:
~A --> B

what you would do is negate both sides
~(~A) --> ~(B)

then switch both sides
~B --> A

Note: two negatives = a positive. ~(~A) = A
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So in this example:
~K --> G

negate both sides:
~(~K) --> ~(G)

then switch both sides:
~G -- > K

Hope this helps!!!


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