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# If f is a function defined for every positive integer x in such a way

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GMATH Teacher
Status: GMATH founder
Joined: 12 Oct 2010
Posts: 935
If f is a function defined for every positive integer x in such a way  [#permalink]

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17 Mar 2019, 12:31
00:00

Difficulty:

35% (medium)

Question Stats:

73% (01:55) correct 27% (01:35) wrong based on 22 sessions

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GMATH practice exercise (Quant Class 3)

_________________
Fabio Skilnik :: GMATH method creator (Math for the GMAT)
Our high-level "quant" preparation starts here: https://gmath.net
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Joined: 06 Feb 2018
Posts: 5
Location: Uzbekistan
Schools: Simon '21
GMAT 1: 650 Q47 V33
GPA: 3.5
Re: If f is a function defined for every positive integer x in such a way  [#permalink]

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17 Mar 2019, 14:58
2
F(X)=(2^8-x)/x^2
F(5)=(2^3)/25=0.32
100*F(5)=32
GMATH Teacher
Status: GMATH founder
Joined: 12 Oct 2010
Posts: 935
Re: If f is a function defined for every positive integer x in such a way  [#permalink]

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17 Mar 2019, 17:36
fskilnik wrote:
GMATH practice exercise (Quant Class 3)

$${x^2} \cdot f\left( x \right) = {2^{8 - x}}\,\,\,\,\left( * \right)$$

$$? = 100 \cdot f\left( 5 \right)$$

$$x = 5\,\,\,\,\,\mathop \Rightarrow \limits^{\left( * \right)} \,\,\,\,\,25 \cdot f\left( 5 \right) = {2^3}\,\,\,\,\mathop \Rightarrow \limits^{ \cdot \,\,4} \,\,\,\,? = 4 \cdot {2^3} = 32$$

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

Regards,
Fabio.
_________________
Fabio Skilnik :: GMATH method creator (Math for the GMAT)
Our high-level "quant" preparation starts here: https://gmath.net
Re: If f is a function defined for every positive integer x in such a way   [#permalink] 17 Mar 2019, 17:36
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