Page 58 - Numbertheory

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n+2 . n :( )

.7 5 4

n + 2 = 140 . 4× 5× 7 = 140

. n = 138

2a3 [AHSME 1967, MAӨ 2009] ( )

. 5b 9 326
8( )
a +b 9 5b 9

6( ) 4( ) 2 ()

9 5b 9 :( )

5b 9 = 5×100 + b ×10 + 9 . 0≤b ≤9
99
= 10(50 + b ) +1 . b =4
9

. 50 + b

9

2a3 = 5b 9 − 326 = 549 − 326 = 223

.a+b = 2+4 = 6 a=2

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