In: Computer Science
Use proof by contrapositive to prove the statement: For all real numbers, if m + n is irrational, then m or n is irrational.
PROOF BY CONTRAPOSITIVE
For example:-
Statement: If A then B (A----->B)
Contrapositive: If not A then not B (~A---->~B)
TRUTH TABLE OF CONTRAPOSITIVE
TO PROVE:- if m+n is an irrational number then m or n is irrational
Statement: if m+n is an irrational number then m or n is irrational
Contrapositive: if m+n is not irrational number then m or n is not irrational
i.e. if m+n is rational number then m or n is a rational number
m + n = p / q (since m+n is a rational no as per contrapositive statement)
m = p/q - n or n= p/q - m
since m+n was a rational number. Therefore any subtraction operation will also yield a rational number
m=rational number or n= rational number.
Hope this helps :)