Well, this one seems to be straightforward, but there are

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Well, this one seems to be straightforward, but there are [#permalink]

12 May 2007, 13:17

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Well, this one seems to be straightforward, but there are some doubts....

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Senior Manager

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12 May 2007, 13:26

you need both statements to solve this one.
2 equations 2 unknowns

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12 May 2007, 13:32

Sergey_is_cool wrote:

you need both statements to solve this one.
2 equations 2 unknowns

But why cannot we guess the values from st1? We've got two sqrds, the difference between which is 16, the first sqrd is greater than the second one: 5^2 - 3^2 = 16. Are there any other sqrds the difference between which can give us 16?

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12 May 2007, 13:42

I would say (C)

a^4-b^4 = (a^2-b^2)(a^2+b^2)

Statement 1

(a^2-b^2)=16

we can plug in but we are still missing (a^2+b^2)

insufficient

Statement 2

(a+b)=8

we are still missing (a^2+b^2)

insufficient

Statement 1&2

Knowing that (a^2-b^2)=(a-b)(a+b)=16

and (a+b)=8

we can plug in and find that (a-b)*8=16

a-b=2 & a+b=8

2b=6

b=3

a=5

so the answer is (C)

:-D

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12 May 2007, 13:43

yeah but you can't just guess numbers you have to have the way to prove that the the equation has only one solution.(It's my guess) Do you have the answer?

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12 May 2007, 13:48

nick_sun wrote:

Sergey_is_cool wrote:

you need both statements to solve this one.
2 equations 2 unknowns

please note that a & b don't have to be integers !!!!!

[#permalink] 12 May 2007, 13:48

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Well, this one seems to be straightforward, but there are

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Well, this one seems to be straightforward, but there are

Well, this one seems to be straightforward, but there are

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