What are the solutions to x^3+3367=2^n?

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In summary, x and n are unknown variables in the equation x^3+3367=2^n, representing a number and a power of 2 respectively. There are multiple solutions to this equation and they can be found using algebraic or numerical methods. This equation has real-life applications in fields such as computer science, cryptography, and physics, helping to solve problems involving exponential growth and patterns.
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anemone
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Here is this week's POTW:

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Determine all positive integers $x,\,n$ that satisfying the equation $x^3+3367=2^n$.

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  • #2
Congratulations to kaliprasad for his correct solution to last week's POTW, which you can find below:

We are given $x^3 + 3367 = 2^n$
Now 3367 = 7 * 13 *37
so let us work mod 7
$x^3 = 2^n \pmod 7$

Working mod 7 we have $x^3 \in \{ 1,-1,0\}$ and $2^n \in \{2,4, 1\}$ so we get common as 2 and for that case n has to be multiple of 3 so say 3m

So we have $x^3 = 2^{3m} \pmod 7$

Going back to the original equation we have
$x^3 + 3367= 2^{3m} \pmod 7$
or $(2^m)^3 - x^3 = 3367$'

We can put $y= 2^m$ to keep it simple
So $y^3-x^3 = 3367$
as $(y-x) | (y^3-x^3$
so y = x = 1 or 7 or 13 or 37
as $(y-x)^2 = (y^2 + x^2 - 2xy) < y^2 + xy + x^2 $ so we have
$(y-x) = 1$ or 7 or 13

By checking y - x = 1 and 13 we do not get any root (method as as below but not mentioned and y-x = 7 gives root as y = 16, x = 9 as below

$ y - x = 7\cdots(1)$
so $y^2 + x^2 + xy = 481$
or $(y-x)^2 + 3xy = 481$
or $7^2 + 3xy = 481$
or $xy = 144\cdots(2)$
From (1) and (2) we get $y=16, x = 9$ or $n=12,x = 9$
 

Related to What are the solutions to x^3+3367=2^n?

1. What is the value of x in the equation x^3+3367=2^n?

The value of x cannot be determined without knowing the value of n. This equation has three variables (x, n, and 3367) and in order to solve for one variable, the other two must be known.

2. Can this equation be solved for all values of n?

Yes, this equation can be solved for all values of n. However, the solutions may not always be integers. In some cases, the solutions may be irrational numbers or complex numbers.

3. How many solutions does this equation have?

This equation has an infinite number of solutions. For every value of n, there will be a corresponding value of x that satisfies the equation.

4. Is there a general formula for finding the solutions to this equation?

Yes, there is a general formula for finding the solutions to this equation. It is called the cubic formula and it involves complex numbers and radicals. However, it is not commonly used due to its complexity.

5. Can this equation be solved without using the cubic formula?

Yes, this equation can be solved without using the cubic formula. It can be solved using numerical methods such as iteration or graphing. It can also be solved using algebraic methods such as factoring or substitution.

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