If you study you will fail
The bellow theorem will tell you that "if you study for exam you will fail"
Normal theory :
case1:If you study you won't fail.
eq-1: study=don't fail;
case2:If you won't study you will fail.
eq-2: don't study=fail;
study+don't study=don't fail+fail;
select common factor out;
cancel (1+don't) on both side
So finally you will get
Hence the theorem was proved.