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# If f(x) = x^2, which of the following is equal to f(m + n) + f(m - n)?

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Math Expert
Joined: 02 Sep 2009
Posts: 51281
If f(x) = x^2, which of the following is equal to f(m + n) + f(m - n)?  [#permalink]

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30 Jul 2018, 23:44
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96% (00:58) correct 4% (00:16) wrong based on 25 sessions

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If $$f(x) = x^2$$, which of the following is equal to $$f(m + n) + f(m - n)$$?

(A) $$m^2 + n^2$$

(B) $$m^2 - n^2$$

(C) $$2m^2 + 2n^2$$

(D) $$2m^2 - 2n^2$$

(E) $$m^2n^2$$

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Math Expert
Joined: 02 Aug 2009
Posts: 7112
Re: If f(x) = x^2, which of the following is equal to f(m + n) + f(m - n)?  [#permalink]

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30 Jul 2018, 23:47
Bunuel wrote:
If $$f(x) = x^2$$, which of the following is equal to $$f(m + n) + f(m - n)$$?

(A) $$m^2 + n^2$$

(B) $$m^2 - n^2$$

(C) $$2m^2 + 2n^2$$

(D) $$2m^2 - 2n^2$$

(E) $$m^2n^2$$

Just be sure you take the square properly..

$$f(m + n) + f(m - n)......(m+n)^2+(m-n)^2=m^2+n^2+2mn+m^2+n^2-2mn=2m^2+2n^2$$...

C
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor

Re: If f(x) = x^2, which of the following is equal to f(m + n) + f(m - n)? &nbs [#permalink] 30 Jul 2018, 23:47
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