Hello, in the explanation of this question I get a bit lost. I see from the answer why d must be -20.25. But when following our typical method of setting discriminant = 0, we get d=20.25. So in this sense, the typical method we use for solving these seems to fail. How do I know when this method will fail, or what approach should be taken to ensure I get d=-20.25 instead of d=20.25?
Coordinate GeometryQ - GRE Quant Problem Solving - Greg Mat+ Community Forum
You can refer to this thread as well.
Basically, you need to cross check your solution, if it is basically changing the requirements or specific constraints.
I see, I was hoping the cross checking wasn’t necessary but it seems like I will just have to be careful of that. Thank you!
Such cases where, by cross checking, the answer changes, is pretty rare in the GRE.
However, it’s always a good habit to cross check the answer.
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