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# If a(x) = 2x^2 + 2, which of the following is equal to a(4)?

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Math Expert
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If a(x) = 2x^2 + 2, which of the following is equal to a(4)?  [#permalink]

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27 Jul 2018, 00:30
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Difficulty:

25% (medium)

Question Stats:

77% (01:04) correct 23% (01:09) wrong based on 48 sessions

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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) $$\alpha(34)$$

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Re: If a(x) = 2x^2 + 2, which of the following is equal to a(4)?  [#permalink]

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27 Jul 2018, 00:49
2
a(x) = $$2x^2 + 2$$

a(x) = $$2(4)^2 + 2$$ = 2(16) + 2 = 34

option A

a(a(-1))

a(-1) = $$2(-1)^2 + 2$$ = 2 + 2 = 4

=> a(a(-1)) = a(4)

Hence option A
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Re: If a(x) = 2x^2 + 2, which of the following is equal to a(4)?  [#permalink]

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27 Jul 2018, 01:21
Starting off with Option A)
= α( α(-1) )
= α( 2*(-1)^2 + 2 )
= α( 2 + 2 )
= α(4)

Hence, A.
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Re: If a(x) = 2x^2 + 2, which of the following is equal to a(4)?  [#permalink]

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27 Jul 2018, 02:05
Ans: A

Question is asking which of these is equal to $$\alpha(4)$$
for not invoilinvg formating i am writting Alpha as F so
give a(x) = 2(x^2 + 1)
we need to find equivalent of a(4); so in other words we don't need to find the value of a(4) just find if the values in the a() is equivalent to 4 or not.. and also check of negatives only because there is no division or substation in the function so value will always increase as the input increases.

Ans: A
Bunuel wrote:
If $$\alpha(x)= 2x^2 + 2$$, which of the following is equal to $$\alpha(4)$$ ?

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Re: If a(x) = 2x^2 + 2, which of the following is equal to a(4)? &nbs [#permalink] 27 Jul 2018, 02:05
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