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

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Math Expert
Joined: 02 Sep 2009
Posts: 58453
The function f is defined by f (x) =√x − 20 for all positive numbers x  [#permalink]

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01 Oct 2018, 23:01
00:00

Difficulty:

25% (medium)

Question Stats:

82% (01:07) correct 18% (02:02) wrong based on 36 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
Joined: 02 Aug 2009
Posts: 7978
Re: The function f is defined by f (x) =√x − 20 for all positive numbers x  [#permalink]

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01 Oct 2018, 23:13
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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Re: The function f is defined by f (x) =√x − 20 for all positive numbers x   [#permalink] 01 Oct 2018, 23:13
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