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# If x is an integer, is 9^x + 9^-x = b? (1)3^x + 3^-x =

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If x is an integer, is 9^x + 9^-x = b? (1)3^x + 3^-x = [#permalink]  22 Sep 2003, 14:34
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25% (01:44) correct 75% (00:51) wrong based on 13 sessions
If x is an integer, is 9^x + 9^-x = b?

(1)3^x + 3^-x = square root of b+2
(2) x>0
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Joined: 03 May 2003
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My attempt [#permalink]  22 Sep 2003, 16:03
If x is an integer, is 9^x + 9^-x = b?

(1)3^x + 3^-x = square root of b+2
(2) x>0

(1)
(3)^x + 1/(3^x) = sqrb+2

square both sides and you get

9^x + 2 + 1/(9^x) = b + 2
subtract 2
and
9^x + 9^-x = b

so 1 is sufficient

(2) in suffient by itself

?
My attempt   [#permalink] 22 Sep 2003, 16:03
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