What is y? 1. y^3 + 2y = y + 2*y^2 2. y^2 = y

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What is y? 1. y^3 + 2y = y + 2*y^2 2. y^2 = y [#permalink]

18 Oct 2007, 14:18

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What is y?

1. y^3 + 2y = y + 2*y^2
2. y^2 = y

CEO

Joined: 21 Jan 2007

Posts: 2797

Location: New York City

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Kudos [?]: 133 [0], given: 4

Re: DS Challenge Roots [#permalink]

18 Oct 2007, 14:19

bmwhype2 wrote:

What is y?

1. y^3 + 2y = y + 2*y^2
2. y^2 = y

1. Set up a quad equation. factor out y. therefore y=0. solve for the rest. y=1.

2. y can be 0 or 1.

Can we have two answers for a DS question?

Manager

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18 Oct 2007, 18:47

ah damn, forgot about the integer 0.

I think the answer is E. y is 0 or 1 for both.

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18 Oct 2007, 18:59

St1:
y^3 + y - 2y^2 = 0
y(y^2 -2y + 1) = 0
y(y-1)^2 = 0
y can be 0 or 1.
Insufficient.

St2:
y^2 - y = 0
y(y-1) = 0
y can be 0 or 1.
Insufficient.

St1 and St2:
Nothing new made known to us. Insufficient.

Ans E

Director

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18 Oct 2007, 20:15

ywilfred wrote:

Agree E it is

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18 Oct 2007, 20:45

I get A...

y=?

(1)

y^3 + 2y=y+2y^2

y(y^2 +2)= y+2y^2

y^2+2=1+2y

y^2-2y+1

(y-1)(y-1) y=1

sufficient

2)

y can be 0 or 1

Director

Joined: 22 Aug 2007

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18 Oct 2007, 20:46

fresinha12 wrote:

I get A...

y=?

(1)

y^3 + 2y=y+2y^2

y(y^2 +2)= y+2y^2

y^2+2=1+2y

y^2-2y+1

(y-1)(y-1) y=1

sufficient

2)

y can be 0 or 1

1) y can be zero as well ..

and given y could be zero the simplification is also invallid...

I always get caught with !zero!

[#permalink] 18 Oct 2007, 20:46

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What is y? 1. y^3 + 2y = y + 2*y^2 2. y^2 = y

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What is y? 1. y^3 + 2y = y + 2*y^2 2. y^2 = y

What is y? 1. y^3 + 2y = y + 2*y^2 2. y^2 = y

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