ext_3099 ([identity profile] griffen.livejournal.com) wrote in [personal profile] kengr 2006-08-19 11:27 pm (UTC)

I know it's wrong, but I can't spot the error.

Oh, wait.

They can't substitute in "a" for "b" in the third line from the bottom. You're solving for A. You can't do that if you monkey around with the variables. This is how it's supposed to fall out:

Given that A = B,

A2 = AB

A2 - B2 = AB - B2

(A + B)(A - B) = B(A-B)

A + B = B

A = 0

Then solve for B:

A = B
A = 0

Therefore, B = 0.

This is why you don't monkey around with the variables.

Post a comment in response:

This account has disabled anonymous posting.
If you don't have an account you can create one now.
HTML doesn't work in the subject.
More info about formatting