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If = 2x2 + 2, which of the following is equal to ? (A) (B) (

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If = 2x2 + 2, which of the following is equal to ? (A) (B) ( [#permalink] New post 25 Jul 2018, 17:17
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Question Stats:

75% (00:27) correct 25% (01:05) wrong based on 8 sessions
If \(\alpha(x)= 2x^2 + 2\), which of the following is equal to \(\alpha(4)\) ?

(A) \(\alpha(\alpha(-1))\)
(B) \(\alpha(-2)\)
(C) \(\alpha(\alpha(2))\)
(D) \(\alpha(17)\)
(E) \(\alpha(34)\)
[Reveal] Spoiler: OA

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Re: If = 2x2 + 2, which of the following is equal to ? (A) (B) ( [#permalink] New post 25 Jul 2018, 20:27
sandy wrote:
If \(\alpha(x)= 2x^2 + 2\), which of the following is equal to \(\alpha(4)\) ?

(A) \(\alpha(\alpha(-1))\)
(B) \(\alpha(-2)\)
(C) \(\alpha(\alpha(2))\)
(D) \(\alpha(17)\)
(E) \(\alpha(34)\)



Given

\(\alpha(x)= 2x^2 + 2\)

we can find out the value of \(\alpha(4)\).

\(\alpha(4)\)

\(\alpha(4) = 2.(4)^2 +2 = 34\)

So we have to find out an answer choice that matches the result.

Option A)

\(\alpha(\alpha(-1))\)

This option has 2 parts. we can segregate them to calculate easily.

\(\alpha(-1) = 2*(-1)^2 + 2 = 4\)

Now we have determine the value of \(\alpha(4)\), which is exactly the same as question stem and we have already found out the value of \(\alpha(4)\)

The best answer is A.
GMAT Club Legend
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Joined: 07 Jun 2014
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Re: If = 2x2 + 2, which of the following is equal to ? (A) (B) ( [#permalink] New post 31 Jul 2018, 14:30
Expert's post
Explanation

To answer the question, “If \(\alpha (x)= 2x^2 + 2\), which of the following is equal to \(\alpha (x)\)?” plug 4 into the given function.
\(\alpha (4)= 2(4)^2 + 2\)
\(\alpha (4)= 34\)

Do not fall for trap answer choice (E). The correct answer is 34, which does not appear in the choices in that form. Trap choice (E) is \(\alpha (34)\) , which equals \(2(34)^2 + 2\); this is much greater than 34.

Instead, solve each answer choice until one equals 34. Choice (A), \(\alpha (\alpha (-1))\), uses the function symbol twice, so plug –1 into the function, then plug the resulting answer back into the function again:
\(\alpha(-1)= 2(–1)^2 + 2 = 4\)
\(\alpha(4)= 2(4)^2 + 2 = 34\)
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Re: If = 2x2 + 2, which of the following is equal to ? (A) (B) (   [#permalink] 31 Jul 2018, 14:30
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