Section 1.2

(For a PDF of this work, click here.)

"If  then ."

If  then .  Therefore if  then .  Now consider:

Thus  needs to have some positive number added to it in order for it to equal ; hence, .

"If  then ."

For the same reason as above, .  Thus we have:

Thus  needs to have some positive value subtracted from it in order to equal ; hence, .