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# Which of the following may be correctly expressed by the graph represe

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GMATH Teacher
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Which of the following may be correctly expressed by the graph represe  [#permalink]

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05 Feb 2019, 14:03
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Difficulty:

65% (hard)

Question Stats:

25% (01:24) correct 75% (01:27) wrong based on 32 sessions

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Which of the following may be correctly expressed by the graph representation given above?

(A) y = |x|^2
(B) y = 2^x
(C) y = x^(-1/2)
(D) y = x^(-1)
(E) y = x^(-2)

GMATH practice exercise (Quant Class 4)

Attachment:

05-Fev19-8j.gif [ 2.5 KiB | Viewed 455 times ]

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Fabio Skilnik :: GMATH method creator (Math for the GMAT)
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Re: Which of the following may be correctly expressed by the graph represe  [#permalink]

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06 Feb 2019, 01:29
This is an exponential curve, where the Y coordinate value decreases as X coordinate value increases.

Only E satisfies.
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Re: Which of the following may be correctly expressed by the graph represe  [#permalink]

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06 Feb 2019, 05:52
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fskilnik wrote:

Which of the following may be correctly expressed by the graph representation given above?

(A) y = |x|^2
(B) y = 2^x
(C) y = x^(-1/2)
(D) y = x^(-1)
(E) y = x^(-2)

GMATH practice exercise (Quant Class 4)

$$?\,\,\,:\,\,\,{\rm{graph}}\,\,{\rm{association}}$$

From the figure given:

> We expect y to decrease whenever |x| increases, in other words, whenever x > 0 gets larger or x < 0 gets smaller (i.e., more negative).
> This is enough to refute (A) and (B).

> We expect y to be defined for all values of x, except when x is zero.
> This is enough to refute (C): when x < 0, x^(-1/2) is not defined.

> We expect y to be positive for all nonzero values of x.
> This is enough to refute (D): when x<0, x^(-1) is negative.

The correct answer is therefore (E), by exclusion!

We follow the notations and rationale taught in the GMATH method.

Regards,
Fabio.

P.S.: more quantitative mature students may also take into account the symmetry related to the y-axis, in the sense that we expect f(x) = f(-x) ...
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Fabio Skilnik :: GMATH method creator (Math for the GMAT)
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Re: Which of the following may be correctly expressed by the graph represe  [#permalink]

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06 Feb 2019, 06:01
fskilnik wrote:

Which of the following may be correctly expressed by the graph representation given above?

(A) y = |x|^2
(B) y = 2^x
(C) y = x^(-1/2)
(D) y = x^(-1)
(E) y = x^(-2)

GMATH practice exercise (Quant Class 4)

Attachment:
05-Fev19-8j.gif

This is a symmetric crve across Y axis ..so positive and negative values of X shouldnt effect .It should hold true and same for either of that.
Next we see as X decreases Y increases ..Option E states y=1/x^2...Means Y is max when X is least and so On..

So choice E
Re: Which of the following may be correctly expressed by the graph represe   [#permalink] 06 Feb 2019, 06:01
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