Question on Lab #2 DS Yes - No Testing

[casey.chopek]

In lab #2, Question 183, the instructor uses the CLA process to answer the question:

Is x^2 greater than x?

1) x^2 is greater than 1
2)x is greater than -1

When listing for statement 1, the instructor lists: 2, 3, 4, 5, 6.

I'm confused as to why he didn't list -2, -3 as well since -2^2 is 4, which is greater than 1.

What am I missing?

Thanks

[StaceyKoprince]

As a general rule, you do want to test negatives when you can - but there is a reason why the instructor didn't bother to test negatives in this case (though he could have explained why!).

Is x^2 > x?

Pick any negative number and square it. What happens? The number becomes positive. Is (any positive number) > (any negative number)? Yes, always - by definition, right? So any negative number you can pick will always give a Y answer.