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Is x > 6? (1) x^2 = 49 (2) 7x = x^2

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Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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New post 27 Feb 2018, 20:17
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

68% (00:42) correct 32% (00:43) wrong based on 104 sessions

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Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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New post 27 Feb 2018, 20:48
Bunuel wrote:
Is x > 6?

(1) x^2 = 49
(2) 7x = x^2


Statement 1:
x=7 / -7 --Insufficient

Statement 2:
\(x^2\) - 7x = 0
x(x-7) = 0
x=0 / 7 --Insufficient

Statement 1 & 2:
x=7 --Sufficient

IMO "C" is correct
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Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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New post 27 Feb 2018, 22:06
Statement 1:

X^2= 49
X= +7/-7
Insufficient

7X=X^2
X(X-7)=0
X= 0,7
Insufficient

Taking both the statement
X=7 sufficient
Ans: C

Correct me if I am wrong .


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Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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New post 10 Mar 2018, 08:07
Hello,

Could we solve Statement #2 this way?
(2) 7x = x^2
7x = x*x
divide both sides by x to get
7=x
Is this correct? and if so, sufficient?
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Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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New post 10 Mar 2018, 08:13
1
francod9 wrote:
Hello,

Could we solve Statement #2 this way?
(2) 7x = x^2
7x = x*x
divide both sides by x to get
7=x
Is this correct? and if so, sufficient?



No you cannot..
You do not whether the variable 'x' is Positive or NEGATIVE..
If NEGATIVE, you can't divide by that variable..

Take it to one side \(7x=x^2…....x^2-7x=0......x(x-7)=0\)
So x can be 0 or 7
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Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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New post 10 Mar 2018, 08:25
chetan2u wrote:
francod9 wrote:
Hello,

Could we solve Statement #2 this way?
(2) 7x = x^2
7x = x*x
divide both sides by x to get
7=x
Is this correct? and if so, sufficient?



No you cannot..
You do not whether the variable 'x' is Positive or NEGATIVE..
If NEGATIVE, you can't divide by that variable..

Take it to one side \(7x=x^2…....x^2-7x=0......x(x-7)=0\)
So x can be 0 or 7



Thank you! :thumbup:
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Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2  [#permalink]

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New post 10 Mar 2018, 10:24
I don't agree with the below statement.
Since (2) 7x = x^2 is an equation, it doesn't matter whether x is negative or positive, we can divide by x on both sides of the equation
But yes we don't know that whether x is zero or non nero number, so we cannot divide by x.

please confirm my understanding.

,
chetan2u wrote:
francod9 wrote:
Hello,

Could we solve Statement #2 this way?
(2) 7x = x^2
7x = x*x
divide both sides by x to get
7=x
Is this correct? and if so, sufficient?



No you cannot..
You do not whether the variable 'x' is Positive or NEGATIVE..
If NEGATIVE, you can't divide by that variable..

Take it to one side \(7x=x^2…....x^2-7x=0......x(x-7)=0\)
So x can be 0 or 7

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Re: Is x > 6? (1) x^2 = 49 (2) 7x = x^2   [#permalink] 10 Mar 2018, 10:24
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