1) x^y= y^z
2) (x)^y-z= 1
Source GMAT Guru 2. OA B)
Is there a general method (ej. pick some numbers) to do this problems? :?
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- JonathanSchneider
- ManhattanGMAT Staff
- Posts: 370
- Joined: Sun Oct 26, 2008 3:40 pm
Depending on the way you've formatted this problem, I'm not sure that B is correct.
Does the original problem show (y-z) as the full exponent of the variable x? If so, it would seem to suggest that (y-z)=0, where x could be anything. However, what if x = -1? In this case, (y-z) could equal anything even. (Note that although you ruled out x = 1, you did not rule out x = -1). As such, B cannot be correct.
Problems of this nature are Number Property problems, specifically Exponents and Roots. While picking numbers is an option, it is generally slow and error-prone. A better approach for Number Properties questions is to understand the specific number property. In this case, for example, we have a variable raised to a certain exponent, all set equal to 1. Rather than pick random numbers, you should see that this leaves us with three options: where the exponent is zero, where the base is 1, or where the base is -1 and the exponent is even. Such criticial thinking (in number property terms) is essential for a quick, correct performance on questions like this one.
Does the original problem show (y-z) as the full exponent of the variable x? If so, it would seem to suggest that (y-z)=0, where x could be anything. However, what if x = -1? In this case, (y-z) could equal anything even. (Note that although you ruled out x = 1, you did not rule out x = -1). As such, B cannot be correct.
Problems of this nature are Number Property problems, specifically Exponents and Roots. While picking numbers is an option, it is generally slow and error-prone. A better approach for Number Properties questions is to understand the specific number property. In this case, for example, we have a variable raised to a certain exponent, all set equal to 1. Rather than pick random numbers, you should see that this leaves us with three options: where the exponent is zero, where the base is 1, or where the base is -1 and the exponent is even. Such criticial thinking (in number property terms) is essential for a quick, correct performance on questions like this one.
- JonathanSchneider
- ManhattanGMAT Staff
- Posts: 370
- Joined: Sun Oct 26, 2008 3:40 pm
4 posts Page 1 of 1