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Very nice explanation Bunuel , thanks a lot !

I was confused whether to choose D or E because i thought that in either of the options x is coming 0 (along with some other value)

But it suggests that the value is not sufficient in both the cases.
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If y does not equal 0. Does x = 0 ?

(1) x^2 y = x^3 y
(2) x^2 / y = x^3 y

please do calrify my doubt :

Given:
y does not equal to zero, does x=0?

x^2y = x^3y

Here we are calculating as x^2y-x^3y
my question is
why can't we do as x^2y/x^3y

Please do clarify when what is the actual procedure and why can't do like this as mentioned later
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skamal7
If y does not equal 0. Does x = 0 ?

(1) x^2 y = x^3 y
(2) x^2 / y = x^3 y

please do calrify my doubt :

Given:
y does not equal to zero, does x=0?

x^2y = x^3y

Here we are calculating as x^2y-x^3y
my question is
why can't we do as x^2y/x^3y

Please do clarify when what is the actual procedure and why can't do like this as mentioned later

Merging similar topics. Please refer to the solutions above.

Also, please read carefully and follow: rules-for-posting-please-read-this-before-posting-133935.html Pay attention to the rule #3.

Next, I guess your question is why are not we dividing both parts of x^2*y = x^3*y by x^3*y to get x^2*y/(x^3*y) = 1. That's because x^3*y can be zero (in case y=0) and we cannot divide by 0.

Hope it's clear.
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gmatopoeia
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Quote:
If y <> = 0 Does x = 0

(1) x^2 y = x^3 y

(2) x^2 / y = x^3 y

Very clear explanation, Bunuel. Thanks!
Initially, I had answer A and realised my mistake after reading Bunuel's solution. My error came from the fact that I cross-multiplied and eliminated as below:
Quote:
From Statement 1
--> x^2y=x^3y --> y/y = x^3/x^2 --> x = 1
Sufficient

Given y does not equal to zero, does x=0?

Statement 1
x^2y = x^3y --> x^3=x^2 --> 0 = x^2(x-1)
So, x=0 or x=1
Insufficient.

Statement 2
x^2/y = x^3y --> 0 = x^2(xy^2-1)
So, x=0 or xy^2=1 (i.e. x is not zero)
Insufficient.

Statement 1 + 2
x^2(x-1) = x^2(xy^2-1)
x-1 = xy^2-1
x(1-y^2) = 0
So, x = 0 or x does not equals to zero (when y^2=1)
Insufficient.

Answer: E

Thank you for the above explanation. However, I'm still confused as to how we are getting from "x^3=x^2 --> 0 = x^2(x-1)". How are we getting to zero on one side? If we divide both sides by x^2, don't we end up 1. Can someone pls clarify? Same for statement 2. Thank you!
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FJ24
gmatopoeia
**
Quote:
If y <> = 0 Does x = 0

(1) x^2 y = x^3 y

(2) x^2 / y = x^3 y

Very clear explanation, Bunuel. Thanks!
Initially, I had answer A and realised my mistake after reading Bunuel's solution. My error came from the fact that I cross-multiplied and eliminated as below:
Quote:
From Statement 1
--> x^2y=x^3y --> y/y = x^3/x^2 --> x = 1
Sufficient

Given y does not equal to zero, does x=0?

Statement 1
x^2y = x^3y --> x^3=x^2 --> 0 = x^2(x-1)
So, x=0 or x=1
Insufficient.

Statement 2
x^2/y = x^3y --> 0 = x^2(xy^2-1)
So, x=0 or xy^2=1 (i.e. x is not zero)
Insufficient.

Statement 1 + 2
x^2(x-1) = x^2(xy^2-1)
x-1 = xy^2-1
x(1-y^2) = 0
So, x = 0 or x does not equals to zero (when y^2=1)
Insufficient.

Answer: E

Thank you for the above explanation. However, I'm still confused as to how we are getting from "x^3=x^2 --> 0 = x^2(x-1)". How are we getting to zero on one side? If we divide both sides by x^2, don't we end up 1. Can someone pls clarify? Same for statement 2. Thank you!

(1) \(x^2=x^3\). (Notice here that we cannot divide this by x^2 to get 1 = x because x can be 0 and we cannot divide by 0. By doing so, we loose the root, namely x = 0, which also satisfies x^2 = x^3)

Rearrange: \(x^3 - x^2 = 0\);

Factor out x^2: \(x^2(x-1)=0\);

Either \(x=0\) or \(x=1\).

(2) \(\frac{x^2}{y}=x^3*y\);

Cross-multiply: \(x^2=x^3y^2\) (the same here: we cannot divide by x^2 to get 1 = xy^2 because x^2 can be zero and we cannot divide by 0.);

Rearrange: \(x^3y^2-x^2=0\);

Factor out x^2: \(x^2(xy^2-1)=0\);

Either \(x=0\) or \(xy^2=1\).
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Thank you so much Bunuel! This clarified my question!
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Bunuel
rxs0005
If y <> = 0 Does x = 0

x^2 y = x^3 y

x^2 / y = x^3 y

Given: \(y\neq{0}\). Question does \(x=0\)?

(1) x^2*y=x^3*y --> as \(y\neq{0}\) we can reduce by \(y\) --> \(x^2=x^3\) --> \(x^2(x-1)=0\) --> either \(x=0\) or \(x=1\). Not sufficient.

(2) x^2/y=x^3*y --> \(x^2=x^3y^2\) --> \(x^2(xy^2-1)=0\) --> either \(x=0\) or \(xy^2=1\) (depending on \(y\) \(x\) can be any positive number). Not sufficient.

(1)+(2) Both \(x=0\) and \(x=1\) (in this case \(y=1\) or \(y=-1\)) satisfy the statements. Not sufficient.

Answer: E.

I don't get it. option B gives us xy^2=1. so x is not equal to 0. so this question is a yes/no question. right??
so option B is sufficient in telling us that x is not equal to 0.

is it necessary to make the option B into an equation of x^2=x^3y^2. ??
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pulak1988
Bunuel
rxs0005
If y <> = 0 Does x = 0

x^2 y = x^3 y

x^2 / y = x^3 y

Given: \(y\neq{0}\). Question does \(x=0\)?

(1) x^2*y=x^3*y --> as \(y\neq{0}\) we can reduce by \(y\) --> \(x^2=x^3\) --> \(x^2(x-1)=0\) --> either \(x=0\) or \(x=1\). Not sufficient.

(2) x^2/y=x^3*y --> \(x^2=x^3y^2\) --> \(x^2(xy^2-1)=0\) --> either \(x=0\) or \(xy^2=1\) (depending on \(y\) \(x\) can be any positive number). Not sufficient.

(1)+(2) Both \(x=0\) and \(x=1\) (in this case \(y=1\) or \(y=-1\)) satisfy the statements. Not sufficient.

Answer: E.

I don't get it. option B gives us xy^2=1. so x is not equal to 0. so this question is a yes/no question. right??
so option B is sufficient in telling us that x is not equal to 0.

is it necessary to make the option B into an equation of x^2=x^3y^2. ??

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