已知

,求下列各式的值:
(1)

; (2)

; (3)

.
(1)8(2)3(3)

(1)

=

=

=7+1=8
(2)∵(

)

=

=7+2=9,又

>0
∴

=3
(3)∵

=

=45,又a>1
∴

=

=3

∴

=(

)(

)=7

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