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

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Joined: 07 Jun 2014
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If = 2x2 + 2, which of the following is equal to ? (A) (B) ( [#permalink]  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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Sandy
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Joined: 06 Jun 2018
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Kudos [?]: 58 [0], given: 0

Re: If = 2x2 + 2, which of the following is equal to ? (A) (B) ( [#permalink]  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 $$\alpha(4)$$

GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4856
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 102

Kudos [?]: 1741 [0], given: 397

Re: If = 2x2 + 2, which of the following is equal to ? (A) (B) ( [#permalink]  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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Sandy
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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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