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# If f(x) = x and g(x) = x^2 + 7 , what is the value of f(g(3)) ?

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Math Expert
Joined: 02 Sep 2009
Posts: 55609
If f(x) = x and g(x) = x^2 + 7 , what is the value of f(g(3)) ?  [#permalink]

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02 Dec 2014, 09:05
00:00

Difficulty:

5% (low)

Question Stats:

91% (00:39) correct 9% (01:11) wrong based on 179 sessions

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Tough and Tricky questions: Functions.

If $$f(x) = \sqrt{x}$$ and $$g(x) = \sqrt{x^2 + 7}$$, what is the value of f(g(3)) ?

A) 1
B) 2
C) 3
D) 4
E) 5

Kudos for a correct solution.

Source: Chili Hot GMAT

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Joined: 13 Jun 2013
Posts: 273
Re: If f(x) = x and g(x) = x^2 + 7 , what is the value of f(g(3)) ?  [#permalink]

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02 Dec 2014, 10:44
1
Bunuel wrote:

Tough and Tricky questions: Functions.

If $$f(x) = \sqrt{x}$$ and $$g(x) = \sqrt{x^2 + 7}$$, what is the value of f(g(3)) ?

A) 1
B) 2
C) 3
D) 4
E) 5

Kudos for a correct solution.

Source: Chili Hot GMAT

$$g(3) =\sqrt{3^2+7}$$
$$g(3)= \sqrt{16}$$
$$g(3)=4$$ (discard -4 because square root of negative numbers are not allowed in gmat.)
thus, $$f(g(3)= \sqrt{4}$$
$$f(g(3)=2$$
hence option B
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Re: If f(x) = x and g(x) = x^2 + 7 , what is the value of f(g(3)) ?  [#permalink]

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02 Dec 2014, 11:16
1
First, calculate g(3) = square root of 9 + 7, which is 4

Now, calculate f(4) = square root of 2

Discard all negative roots because GMAT accepts only positive roots.

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Re: If f(x) = x and g(x) = x^2 + 7 , what is the value of f(g(3)) ?  [#permalink]

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02 Dec 2014, 18:51
1

$$f(x) = \sqrt{x}$$ and $$g(x) = \sqrt{x^2 + 7}$$

$$f(g(x)) = (\sqrt{x^2 + 7})^{(\frac{1}{2})} = (x^2 + 7)^{(\frac{1}{4})}$$

$$f(g(3)) = (3^2 + 7)^{(\frac{1}{4})} = (2^4)^{(\frac{1}{4})} = 2$$
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Math Expert
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Posts: 55609
Re: If f(x) = x and g(x) = x^2 + 7 , what is the value of f(g(3)) ?  [#permalink]

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03 Dec 2014, 07:48
Bunuel wrote:

Tough and Tricky questions: Functions.

If $$f(x) = \sqrt{x}$$ and $$g(x) = \sqrt{x^2 + 7}$$, what is the value of f(g(3)) ?

A) 1
B) 2
C) 3
D) 4
E) 5

Kudos for a correct solution.

Source: Chili Hot GMAT

Check other function questions in our Special Questions Directory:

Operations/functions defining algebraic/arithmetic expressions
Symbols Representing Arithmetic Operation
Rounding Functions
Various Functions
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Joined: 13 Jul 2017
Posts: 29
Re: If f(x) = x and g(x) = x^2 + 7 , what is the value of f(g(3)) ?  [#permalink]

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01 Aug 2017, 08:37
Very Easy just 20 second question
option B
g(3)=√3^2+7
g(3)=√9+7
g(3)=√16=4
now put 4 in f(x)
f(4)=√4=2
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Re: If f(x) = x and g(x) = x^2 + 7 , what is the value of f(g(3)) ?  [#permalink]

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29 Dec 2018, 11:33
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Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: If f(x) = x and g(x) = x^2 + 7 , what is the value of f(g(3)) ?   [#permalink] 29 Dec 2018, 11:33
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