The Powers of 2014 Unleashed!

Algebra Level 5

The remainder when 2014 2029105 { 2014 }^{ 2029105 } is divided by ( 2014 2014 1 ) ({ 2014 }^{ 2014 }-1) can be expressed as a b { a }^{ b } . If a , b a,b are integers. Find a + b a+b


The answer is 3021.

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3 solutions

Tasmeem Reza
Dec 23, 2014

201 4 2014 1 0 mod ( 201 4 2014 1 ) 2014^{2014}-1\equiv 0 \; \textrm{mod} \; (2014^{2014}-1) 201 4 2014 1 mod ( 201 4 2014 1 ) \Rightarrow 2014^{2014}\equiv 1 \; \textrm{mod} \; (2014^{2014}-1) ( 201 4 2014 ) 1007 1 1007 1 mod ( 201 4 2014 1 ) \Rightarrow \left ( 2014^{2014} \right )^{1007} \equiv 1^{1007} \equiv 1 \; \textrm{mod} \; (2014^{2014}-1) 201 4 2028098 1 mod ( 201 4 2014 1 ) \Rightarrow 2014^{2028098}\equiv 1 \; \textrm{mod} \; (2014^{2014}-1) 201 4 2028098 × 201 4 1007 1 × 201 4 1007 mod ( 201 4 2014 1 ) \Rightarrow 2014^{2028098} \times 2014^{1007} \equiv 1 \times 2014^{1007} \; \textrm{mod} \; (2014^{2014}-1) 201 4 2029105 201 4 1007 mod ( 201 4 2014 1 ) \Rightarrow 2014^{2029105} \equiv 2014^{1007} \; \textrm{mod} \; (2014^{2014}-1) As, 201 4 1007 < 201 4 2014 1 , 201 4 1007 2014^{1007} < 2014^{2014}-1, \; \; 2014^{1007} is the desired reminder. Thus the answer is 2014 + 1007 = 3021 2014+1007=\boxed{3021}

Chew-Seong Cheong
Dec 23, 2014

201 4 2029105 = 201 4 1007 × 2014 + 1007 = 201 4 1007 201 4 1007 × 2014 2014^{2029105} = 2014^{1007\times 2014 + 1007} = 2014^{1007} 2014^{1007\times 2014}

= 201 4 1007 [ ( 201 4 2014 1 ) n = 0 1006 201 4 2014 n 1 ] \quad \quad \quad \quad \quad = 2014^{1007} \left[ (2014^{2014}-1) \displaystyle \sum _{n=0} ^{1006} {2014^{2014n}}-1 \right]

= 201 4 1007 ( 201 4 2014 1 ) n = 0 1006 201 4 2014 n 201 4 1007 \quad \quad \quad \quad \quad = 2014^{1007} (2014^{2014}-1) \displaystyle \sum _{n=0} ^{1006} {2014^{2014n}}-2014^{1007}

Therefore, 201 4 2029105 201 4 1007 ( m o d 201 4 2014 ) \quad 2014^{2029105} \equiv 2014^{1007} \pmod {2014^{2014}}

a = 2014 \quad \quad \quad \quad \quad \Rightarrow a = 2014 and b = 1007 a + b = 3021 b = 1007\quad \Rightarrow a+b = \boxed {3021}

Mehul Chaturvedi
Dec 23, 2014

Just observe a series for small nos. first

( 3 5 ) m o d ( 3 3 1 ) = ( 3 5 m o d 3 ) ( 4 7 ) m o d ( 4 4 1 ) = ( 4 7 m o d 4 ) . . . . . . a b m o d a a = a b m o d a { 201 4 2029105 } m o d { ( 201 4 2014 ) 1 } = 201 4 2029105 m o d 2014 i . e 201 4 1007 a + b = 3021 \large{\Rightarrow (3^{ 5 })mod(3^{ 3 }-1)=(3^{ 5~ mod~ 3 })\\ \Rightarrow (4^{ 7 })~ mod~ (4^{ 4 }-1)=(4^{ 7~ mod~ 4 })\\ ..\\ ..\\ ..\\ \Rightarrow a^{ b }~ mod~ a^{ a }=a^{ b~ mod~ a }\\ \Rightarrow \{ 2014^{ 2029105 }\} ~ mod~ \{ (2014^{ 2014 })-1\} =2014^{ 2029105~ mod~ 2014 }\\ \Rightarrow i.e\quad 2014^{ 1007 }\\ \Rightarrow \boxed { a+b=3021 } }

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