Base five nuneration system

Algebra Level 2

5 x + 1 + 5 1 x = 26 \large 5^{x+1} + 5^{1-x} = 26

Find the sum of all values of x x that satisfy the equation above.


The answer is 0.

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7 solutions

Sandeep Bhardwaj
Aug 22, 2014

Let 5 x = y 5^{x} =y

. So given eqn becomes 5 y + 5 y = 26 5y + \frac{5}{y} = 26

5. y 2 26 y + 5 = 0 \implies 5.y^{2} - 26 y + 5 =0

( y 5 ) ( y 1 5 ) = 0 (y-5)(y-\frac{1}{5})=0 .

y = 5 o r y = 1 5 \therefore y=5 \ or \ y=\frac{1}{5}

so x = 1 o r x = 1 x=1 \ or \ x=-1

Hence + 1 1 = 0 +1-1 = \boxed{0} .

enjoy!

what about x=1 ? Pls check this equation with x=1....

Arun Vijayan - 5 years, 4 months ago

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5^x+1 + 5^x-1 = 26. x can also be 1. if x is equal to 1 then 5^1+1 + 5^1-1 = 26 <=> 5^2 + 5^0=26 <=> 25 + 1 = 26 Arun Vijayan 1 was also my answer you are correct.

Francisco Rosa - 5 years, 4 months ago

i do not agree.. try to check the answer to the given equation.. substitute 0 to x..is it equal to "26"?? i don't think so..

Angelo Supleo - 6 years, 2 months ago

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Angelo Supelo the SUM of solutions is asked

A Former Brilliant Member - 6 years, 2 months ago

5^1+5^1=10 x should be 1

Arpit Gupta - 6 years ago

if your answer is x=o, 5 to the (0+1) + 5 to the (1-x) =26 then 5 to the 1 + 5 to the 1 = 26, then 5+5 = 26, then 10 not equal to 26. So wrong answer if zero.

Juan Cruz - 6 years, 2 months ago

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what was asked was the sum of the solutions, not the solution. The solution was perfectly correct.

Daniel Angelo Reyes Mirador - 6 years, 2 months ago
Morgan Blake
Apr 2, 2015

Note that the equation is symmetric in x x and x -x . Hence, if x = a x=a is a solution, then so is x = a x=-a . So, the sum of all solutions is zero.

Lew Sterling Jr
Apr 3, 2015

Steps for this question.

Steps for this question (just by plugging in).

Cleres Cupertino
Jan 19, 2016

Let´s Think about it...

5 ( x + 1 ) + 5 ( 1 x ) = 26 = 25 + 1 = 5 2 + 5 0 5^{(x+1)} + 5^{(1-x)} = 26 = 25 + 1 = 5^2+5^0

\implies { ( x + 1 ) = 2 (x+1) = 2 and ( 1 x ) = 0 (1-x) = 0 } or { ( x + 1 ) = 0 (x+1) = 0 and ( 1 x ) = 2 (1-x) = 2 }

\implies { x = 1 x = 1 and 1 = x 1 = x } or { x = 1 x = -1 and 1 = x -1 = x }

So, x = { 1 , 1 } x=\{-1,1\}

Achille 'Gilles'
Jan 19, 2016

Considering the result is ending with 6 and any product of 5 will end with a 5. Therefore a 1 is needed in the addition so one of the exponant has to be 0.

Ubaidullah Khan
Apr 2, 2015

I have just put the values (1,-1) and checked the equation. When we add them they become Zero (0).

Godwin Tom George
Sep 21, 2014

Just split 26 as 5^2+5^0

Equate (x+1)=2

Then equate (x+1)=0

Since there are the two solution,we can conclude that the solutions 1 and -1 respectively

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