A number Theory Question: Solve 2^x=3^y+509 over positive integers

  • #1
littlemathquark
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Homework Statement
Question about number theory
Relevant Equations
Solve ##2^x=3^y+509## over positive integers.
My attempt and solution :
$$2^x=3^y+509\Longrightarrow 2^x-512=3^y+509-512\Longrightarrow 2^x-2^9=3^y-3$$
$$\Longrightarrow 2^9(2^{x-9}-1)=3(3^{y-1}-1)$$
$$\Longrightarrow (x,~y)=\boxed{(9,~1)}$$
İs there any solution?
 
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  • #2
İf $$x>9$$ and $$y>1$$ then another solution let $$a,b\in\mathbb{Z^+}$$ $$(9+a,1+b)$$. Because of ##2^{a+9}=3^{b+1}+509## and ##2^9=3+509## $$2^a(3+509)=509+3^{b+1}$$ $$(2^a-1)509=3(3^b-2^a)$$ But 3 and 509 numbers prime so $$2^a-1=3$$ and $$3^b-2^a=509$$ . But in that case $$3^b=513$$ so b not be a positive number. Hence only solution is ##(9,1)##
 

FAQ: A number Theory Question: Solve 2^x=3^y+509 over positive integers

What is the equation we are trying to solve?

The equation we are trying to solve is 2^x = 3^y + 509, where x and y are positive integers.

What does it mean to solve the equation over positive integers?

Solving the equation over positive integers means finding all pairs of positive integer values (x, y) that satisfy the given equation.

Are there any specific methods to approach this type of number theory problem?

Yes, common methods include modular arithmetic, bounding techniques, and sometimes using properties of exponential functions to find possible values for x and y. One might also check specific small values of y and see if the corresponding x is an integer.

What are the possible values for x and y that satisfy the equation?

To find the possible values for x and y, one can start testing small values for y. For example, if y = 1, then 3^1 + 509 = 512, which is 2^9. Thus, (x, y) = (9, 1) is one solution. Further investigation is needed to check if there are other solutions for larger values of y.

Is there a systematic way to prove whether there are more solutions?

Yes, one can use bounds and properties of exponential growth to argue that for large values of y, 3^y grows faster than 2^x, thus limiting the possible solutions. A detailed analysis or proof by contradiction may be required to show that (9, 1) is the only solution in positive integers.

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