what is the value of x+y?

Question

1) x^2 + y^2 + xy = 7
2) 3xy + 1 = 7

GMATbuster's Collection

iPrasad · Answer

Statement I: x^2 + y^2+xy = 7
not sufficient
Statement II: xy = 2
not sufficient

Both together:
adding 1 & 2, we get
x^2+ y ^2+2xy = 9
(x + y)^2 = 9
x+y =  + 3

Not sufficient

Answer: E

CrackverbalGMAT · Answer

In this question, we need to find a unique value for the expression x+y. Any data that helps us do this will be sufficient data.

There are two ways to find a unique value for x+y:

The solution of the question can be summarized as shown in the diagram below:

Attachment:

14th Aug 2019 - Reply 3.JPG [ 66.8 KiB | Viewed 2316 times ]

Clearly, answer option C is the trap answer here, for all of us who are not careful in the last step.

Remember, \(x^2\) = \(a^2\) always means x = ± a. So, \((x+y)^2\) = 9 means (x+y) = ± 3.

The correct answer option is E.

Hope this helps!

what is the value of x+y?

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