Which of the following lines in the xy-plane does not contai

Question

Which of the following lines in the xy-plane does not contain any point with two negative coordinates?

(A) y = x
(B) y = x + 10
(C) y = x^2 - 2
(D) y = x^3 + x
(E) y = x^4

Source:  GMAT Hacks -100413

I was confused between C & E.

Qoofi · Answer

Hi avohden,

For this question, Option A, B, & D are ruled out.

Now lets take Option C : y = x^2 - 2 
here when x = -1 , y = -1 ( 2 Negative Co ordinates)

Option E : y = x^4.
Whatever the value of x ( -ve o r+ve), value of y is always positive.

Hence the answer is option E

jlgdr · Answer

Just picture this. Try plugging y negatives to get x negatives Obviously when one has a fourth power result will never be negative Hence E is the correct answer Cheers! J

EMPOWERgmatRichC · Answer

Hi All,

This question can be solved with Graphing, Number Properties and/or by TESTing VALUES. The question is phrased in such a way that you should NOT be TESTing random values though - you should be purposely choosing values to eliminate answer choices. Here's how:

We're asked to find an equation that has NO point (a set of co-ordinates) that are BOTH NEGATIVE. Let's go try to find that EXACT THING in each of the 5 choices:

A: Y = X
IF....
X = -1, Y = -1
These are BOTH NEGATIVE. Eliminate A.

B: Y = X + 10
IF....
X = -11, Y = -1
These are BOTH NEGATIVE. Eliminate B.

C: Y = X^2 - 2
IF....
X = -1, Y = -1
These are BOTH NEGATIVE. Eliminate C.

D: Y = X^3 + X
IF...
X = -1, Y = -2
These are BOTH NEGATIVE. Eliminate D.

By extension, there's only one answer left....the correct one.

Final Answer:  E

GMAT assassins aren't born, they're made,
Rich

tarangchhabra · Answer

Hi,
One thing to keep in mind is: A perfect square can never obtain a negative value (unless we are dealing with imaginary numbers, which is not the case in GMAT)

Thus a pefect square is greater than or equal to zero!

In option (E), 
y is equal to a perfect square!
Thus (E) is the desired answer as y can never be negative!

bumpbot · Answer

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Which of the following lines in the xy-plane does not contai

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