stonecold wrote:
Is x=y?
[A] x² = xy
x² = y²
Vyshak's solution is great, so I won't re-answer the question.
I just want to point out that the intended TRAP here is that some people will
incorrectly take the equation x² = xy and divide both sides by x to get x = y
People who do that will incorrectly conclude that the answer is A.
The problem with taking the equation x² = xy and dividing both sides by x is that you may be dividing both sides by zero, which is a big no-no.
Likewise, if we take this valid equation, (2)(0) = (1)(0) and divide both sides by 0, we can't then conclude that 2 = 1
Cheers,
Brent
Can we conclude that, for this similar questions, it is easier if we use algebraic approach?
There's an app for that - Steve Jobs.