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Algebra Difficulty 5.7 AIME, harder Find the answer

Solve in positive real numbers: n+n+n3=2014n+ \lfloor \sqrt{n} \rfloor+\lfloor \sqrt[3]{n} \rfloor=2014

A number or a short expression. Spacing and $ signs are ignored.

Solution

We are asked to solve the equation n+n+n3=2014 n+ \lfloor \sqrt{n} \rfloor + \lfloor \sqrt[3]{n} \rfloor = 2014 for positive real numbers n n .

To begin, we denote:
- x=n x = \lfloor \sqrt{n} \rfloor ,
- y=n3 y = \lfloor \sqrt[3]{n} \rfloor .

Thus, we have:
xn<x+1 x \leq \sqrt{n} < x+1
yn3<y+1 y \leq \sqrt[3]{n} < y+1

Therefore,
x2n<(x+1)2 x^2 \leq n < (x+1)^2
y3n<(y+1)3 y^3 \leq n < (y+1)^3

Substituting these into the original equation, we have:
n+x+y=2014 n + x + y = 2014

Next, we will approximate values to find the range for n n .

1. **Approximate n\sqrt{n} and n3\sqrt[3]{n}**

Since x=n x = \lfloor \sqrt{n} \rfloor and y=n3 y = \lfloor \sqrt[3]{n} \rfloor , assume that:
nx2andny3 n \approx x^2 \quad \text{and} \quad n \approx y^3

2. **Estimate n n :**

From the equation, n+x+y=2014 n + x + y = 2014 , express x x and y y in terms of n n :
xnandyn3 x \approx \sqrt{n} \quad \text{and} \quad y \approx \sqrt[3]{n}

Substituting:
n+n+n32014 n + \sqrt{n} + \sqrt[3]{n} \approx 2014

Let's try some approximate calculations:

3. **Trial Calculation for n n :**

Suppose n=1958 n = 1958 , then:
195844.231958=44 \sqrt{1958} \approx 44.23 \quad \Rightarrow \quad \lfloor \sqrt{1958} \rfloor = 44
1958312.5719583=12 \sqrt[3]{1958} \approx 12.57 \quad \Rightarrow \quad \lfloor \sqrt[3]{1958} \rfloor = 12

Hence,
1958+44+12=2014 1958 + 44 + 12 = 2014

This satisfies the equation.

Thus, the solution to the equation in positive real numbers is:
1958 \boxed{1958}

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Source: Omni-MATH, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.