Help me, I am new to discrete math
I was lost in the first day of class. He listed all the axiom from 1 to 13. Then he start proving things. For example:
Theorm
For all real number X
The additive inverse -X is unique.
Proof
Let Y and Z be additive inverse of X.
Y = Y + 0....................( axion 5, additive identity )
Y = Y + ( X + Z )..........( Z is additive inverse of X )
Y = (Y + X ) + Z...........( axion 3, associative law )
Y = 0 + Z.....................( Y is additive inverse of X )
Y = Z .........................( 0 is additive identity )
The prove above. I understand perfectly.
Here are some of the things that I need to prove but I don't know how to prove. Please teach/tell me how to do the following questions.
Question 3:
Prove that ( -X * Y ) is equal to ( X * -Y )
Question 6:
if X + Z = Y + Z prove that X equal to Y
Questions are from [link removed]
If you teach me how to do that those 2 question, I think i know how to do the rest hopefully.
Edited: To clarify, I was in a rush before