Question

Discrete Math Course. Prove with the element method or analytical method using identities from p.355. or disprove with a counter example AXB ⊆ AXC then B ⊆ C

Answer 1

True .  We will prove it by element method .

Proof : First we choose an element from   say .

Let .

   [ since ]

and

  

So    implies   ,

Hence ,

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If you have any doubt please comment .