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# If f(x) = x2 – 1, what is the value of f(y) + f(–1)?

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Retired Moderator
Joined: 07 Jun 2014
Posts: 4803
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
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Kudos [?]: 2911 [0], given: 394

If f(x) = x2 – 1, what is the value of f(y) + f(–1)? [#permalink]  25 Jul 2018, 17:12
Expert's post
00:00

Question Stats:

96% (00:24) correct 3% (00:48) wrong based on 28 sessions
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) $$y^2 - 2y - 1$$
[Reveal] Spoiler: OA

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Sandy
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Retired Moderator
Joined: 07 Jun 2014
Posts: 4803
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 171

Kudos [?]: 2911 [0], given: 394

Re: If f(x) = x2 – 1, what is the value of f(y) + f(–1)? [#permalink]  31 Jul 2018, 14:22
Expert's post
Explanation

The question requires plugging y into the function, then plugging –1 into the function, then summing the two results:

$$f(y) = y^2 - 1$$
$$f(-1) = (-1)^2 - 1$$
$$f(-1) = 0$$

Thus, $$f(y) + f(-1) = y^2 - 1 + 0 = y^2 - 1$$.
_________________

Sandy
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Re: If f(x) = x2 – 1, what is the value of f(y) + f(–1)?   [#permalink] 31 Jul 2018, 14:22
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