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Math Expert V
Joined: 02 Sep 2009
Posts: 62496
If f(x) = k(x - k) and k is a constant, what is the value of f(4) - f  [#permalink]

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Question Stats: 100% (01:13) correct 0% (00:00) wrong based on 26 sessions

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If f(x) = k(x - k) and k is a constant, what is the value of f(4) - f(3), in terms of k?

(A) 1
(B) k
(C) 7k - 1
(D) k^2 + k
(E) k^2 - k

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Senior Manager  G
Joined: 14 Dec 2019
Posts: 494
Location: Poland
GMAT 1: 570 Q41 V27
WE: Engineering (Consumer Electronics)
Re: If f(x) = k(x - k) and k is a constant, what is the value of f(4) - f  [#permalink]

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If f(x) = k(x - k) and k is a constant, what is the value of f(4) - f(3), in terms of k?

(A) 1
(B) k
(C) 7k - 1
(D) k^2 + k
(E) k^2 - k

f(4) = k(4-k); f(3) = k(3-k)

f(4) - f(3) = 4k-$$k^2$$-3k+$$k^2$$ -> k - Answer - B
GMAT Club Legend  V
Joined: 11 Sep 2015
Posts: 4579
GMAT 1: 770 Q49 V46
Re: If f(x) = k(x - k) and k is a constant, what is the value of f(4) - f  [#permalink]

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Top Contributor
Bunuel wrote:
If f(x) = k(x - k) and k is a constant, what is the value of f(4) - f(3), in terms of k?

(A) 1
(B) k
(C) 7k - 1
(D) k^2 + k
(E) k^2 - k

Given: f(x) = k(x - k)
So, for example, f(9) = k(9 - k) = 9k - k²

The question asks for the value of f(4) - f(3)
f(4) - f(3) = [k(4 - k)] - [k(3 - k)]
= [4k - k²] - [3k - k²]
= k

Cheers,
Brent
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Joined: 03 Jun 2019
Posts: 2502
Location: India
GMAT 1: 690 Q50 V34 WE: Engineering (Transportation)
Re: If f(x) = k(x - k) and k is a constant, what is the value of f(4) - f  [#permalink]

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Bunuel wrote:
If f(x) = k(x - k) and k is a constant, what is the value of f(4) - f(3), in terms of k?

(A) 1
(B) k
(C) 7k - 1
(D) k^2 + k
(E) k^2 - k

f(4) = k(4-k)
f(3) = k(3-k)
f(4) - f(3) = k

IMO B Re: If f(x) = k(x - k) and k is a constant, what is the value of f(4) - f   [#permalink] 06 Feb 2020, 07:26
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# If f(x) = k(x - k) and k is a constant, what is the value of f(4) - f  