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If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 fo 28 Apr 2021, 06:30
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58% (01:02) correct 42% (01:10) wrong based on 193 sessions

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If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 for x < 0, what is the value of f (k)?

(1) |k| = 3
(2) k < 0
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A
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If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 fo 28 Apr 2021, 06:49
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Bunuel
If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 for x < 0, what is the value of f (k)?

(1) |k| = 3
(2) k < 0
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IMO the answer is option E

With state 1 : we get +3 and -3 which will give 2 different values 1st function.. insufficient
State 2 says k<0 but does not specify the value . insufficient

By combining we get k<0 and k=-3
we get two diff values again for both the functions
Therefore, answer is option E
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GMAT 1: 780 Q51 V45
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If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 fo 28 Apr 2021, 12:29
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Bunuel
If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 for x < 0, what is the value of f (k)?

(1) |k| = 3
(2) k < 0
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This is a split function so it is important to know which part of the region k lies in.

Statement 1:

If k = 3, we get \(f(3) = 27*3 = 81\). If k = -3, we get \(f(-3) = (-3)^4 = 81\).

Therefore, either way, we get the same value. Sufficient.

Statement 2:

Insufficient.

Ans: A
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If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 fo 01 May 2021, 08:46
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ManyataM
Bunuel
If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 for x < 0, what is the value of f (k)?

(1) |k| = 3
(2) k < 0


IMO the answer is option E

With state 1 : we get +3 and -3 which will give 2 different values 1st function.. insufficient
State 2 says k<0 but does not specify the value . insufficient

By combining we get k<0 and k=-3
we get two diff values again for both the functions
Therefore, answer is option E
Show more
Hi ManyataM

For Statement -1, you are right that value of K is + 3
But question is to find value of f (k).

so in both cases answer is 81.
i.e. GIVEN INFORMATION is SUFFICIENT to find the answer.
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If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 fo 01 May 2021, 08:52
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ramlala
ManyataM
Bunuel
If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 for x < 0, what is the value of f (k)?

(1) |k| = 3
(2) k < 0


IMO the answer is option E

With state 1 : we get +3 and -3 which will give 2 different values 1st function.. insufficient
State 2 says k<0 but does not specify the value . insufficient

By combining we get k<0 and k=-3
we get two diff values again for both the functions
Therefore, answer is option E
Hi ManyataM

For Statement -1, you are right that value of K is + 3
But question is to find value of f (k).

so in both cases answer is 81.
i.e. GIVEN INFORMATION is SUFFICIENT to find the answer.
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How will we calculate for the first expression?
27 * x ??

Posted from my mobile device
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If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 fo 01 May 2021, 08:58
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ManyataM


How will we calculate for the first expression?
27 * x ??

Posted from my mobile device
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Hi ManyataM
Please see the question.
There are two condition

Quote:
If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 for x < 0, what is the value of f (k)?

(1) |k| = 3
(2) k < 0
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When k=3
f(k) = 27 * 3 = 81

and
When k=(-3)
f(k) = \((-3)^4\) = 81

In both values of k, Ans is 81.
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If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 fo 15 Jul 2021, 09:02
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I drew a rough graph for this question.

Source: Wolfram

\(f(k)=\)?

S1: \(|k|=3 \implies k=\pm 3\)
From the graph, it's clear that \(f(k)=f(-k)\)
Consider, \(f(3)=27*3=(-3)^4=f(-3)\)
Sufficient

S2: \(k < 0\)
Insufficient

Hence A
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If f is the function defined by f(x) = 27x for x ≥ 0 and f(x) = x^4 fo 04 Apr 2026, 00:24
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nah bro, if u combine both (1) and (2), you'll only get -3 and u will only plug it into x^4 since it's for x<0. So i dont think that it's E
ManyataM



IMO the answer is option E

With state 1 : we get +3 and -3 which will give 2 different values 1st function.. insufficient
State 2 says k<0 but does not specify the value . insufficient

By combining we get k<0 and k=-3
we get two diff values again for both the functions
Therefore, answer is option E
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