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# If f(x) = x^2 – 1, what is the value of f(y) + f(–1)?

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If f(x) = x^2 – 1, what is the value of f(y) + f(–1)?  [#permalink]

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27 Jul 2018, 01:12
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Difficulty:

5% (low)

Question Stats:

88% (00:32) correct 13% (00:48) wrong based on 40 sessions

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If $$f(x) = x^2 - 1$$, what is the value of $$f(y) + f(-1)$$?

(A) $$y^2 - 1$$
(B) $$y^2$$
(C) $$y^2 + 1$$
(D) $$y^2 - 2y$$
(E) $$y^2 - 2y - 1$$

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Re: If f(x) = x^2 – 1, what is the value of f(y) + f(–1)?  [#permalink]

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27 Jul 2018, 01:20
$$f(x) = x^2 - 1$$
$$f(y) = y^2 - 1$$
$$f(-1) = (-1)^2 - 1 = 1 - 1 = 0$$

$$f(y) + f(-1) = f(y) = y^2 - 1$$
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Re: If f(x) = x^2 – 1, what is the value of f(y) + f(–1)?  [#permalink]

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27 Jul 2018, 02:04
= f(y) + f(−1)
= ( y^2 - 1) + ( (-1)^2 - 1 )
= y^2 - 1 + 0
= y^2 - 1

Hence, A.
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Re: If f(x) = x^2 – 1, what is the value of f(y) + f(–1)?  [#permalink]

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27 Jul 2018, 05:10
f(x) = x^2 – 1
f(y) = y^2 - 1
f(-1) = (-1)^2 - 1 = 0

f(y) + f(–1) = y^2 - 1

IMO A
Re: If f(x) = x^2 – 1, what is the value of f(y) + f(–1)? &nbs [#permalink] 27 Jul 2018, 05:10
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