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#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  # The function f is defined by f (x) =√x − 20 for all positive numbers x

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Math Expert V
Joined: 02 Sep 2009
Posts: 65187
The function f is defined by f (x) =√x − 20 for all positive numbers x  [#permalink]

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Difficulty:   15% (low)

Question Stats: 82% (01:14) correct 18% (01:41) wrong based on 84 sessions

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The function f is defined by f (x) =√x − 20 for all positive numbers x. If p = f(q) for some positive numbers q and p, what is q in terms of p?

(A) (p + 20)^2

(B) √(p + 20)

(C) (√p + 20)^2

(D) √(p^2 + 20)

(E) (p^2 + 20)^2

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Math Expert V
Joined: 02 Aug 2009
Posts: 8757
Re: The function f is defined by f (x) =√x − 20 for all positive numbers x  [#permalink]

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Bunuel wrote:
The function f is defined by f (x) =√x − 20 for all positive numbers x. If p = f(q) for some positive numbers q and p, what is q in terms of p?

(A) (p + 20)^2

(B) √(p + 20)

(C) (√p + 20)^2

(D) √(p^2 + 20)

(E) (p^2 + 20)^2

$$f(q)=√q-20=p.............√q=p+20.......q=(p+20)^2$$...A

OR

Take p=1, so √q-20=1.....q=(20+1)^2
Look in choices
Only A matches
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Intern  B
Joined: 26 May 2020
Posts: 8
Re: The function f is defined by f (x) =√x − 20 for all positive numbers x  [#permalink]

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chetan2u Hi

How did you get from √q−20=p to √q=p+20 since we cannot separate the root?

Thank you
Target Test Prep Representative V
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 11083
Location: United States (CA)
Re: The function f is defined by f (x) =√x − 20 for all positive numbers x  [#permalink]

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Bunuel wrote:
The function f is defined by f (x) =√x − 20 for all positive numbers x. If p = f(q) for some positive numbers q and p, what is q in terms of p?

(A) (p + 20)^2

(B) √(p + 20)

(C) (√p + 20)^2

(D) √(p^2 + 20)

(E) (p^2 + 20)^2

Simplifying, we have:

√q − 20 = p

√q = p + 20

q = (p + 20)^2

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# The function f is defined by f (x) =√x − 20 for all positive numbers x  