# A tricky problem with a "divine" answer!

TLDRIn this video, Presh Talwalkar presents a mathematical problem where the solution leads to a 'divine' result. The problem involves solving for real values of x in an equation with square roots. Through a series of clever substitutions and simplifications, the quadratic equation is solved using the quadratic formula. After eliminating the negative root, the solution is revealed to be the golden ratio, offering a unique and elegant conclusion. This mathematical journey showcases a fascinating connection to a famous constant.

### Takeaways

- 🤔 The problem involves solving for real values of x in a complex equation involving square roots and fractions.
- 🧮 Clever substitutions are used: the first term is assigned as 'a' and the second term as 'b', simplifying the equation to a + b = x.
- ✖️ Multiplying both sides by (a - b) leads to a difference of squares: a² - b² = x(a - b).
- 🔄 Simplifying a² and b², we substitute into the equation to get x - 1 = a² - b².
- 📐 The equation is then manipulated and rearranged, leading to two new expressions, which are further simplified.
- 📊 By adding these equations together, the b terms cancel out, giving us an equation for 'a'.
- ⚙️ Solving a quadratic equation results in two potential roots: the golden ratio and its negative reciprocal.
- ❌ The negative reciprocal of the golden ratio is discarded as a solution because the sum of two square roots must be non-negative.
- ✅ The golden ratio is confirmed to be the correct solution to the original equation.
- ✨ The golden ratio, known as a 'divine' answer, is the final solution to the problem.

### Q & A

### What is the equation given in the problem?

-The equation is (x - 1/x)^(1/2) + (1 - 1/x)^(1/2) = x.

### What are the clever substitutions used to simplify the problem?

-The first term (x - 1/x)^(1/2) is substituted as 'a' and the second term (1 - 1/x)^(1/2) as 'b', simplifying the equation to a + b = x.

### How is the equation transformed using a difference of squares?

-By multiplying both sides of the equation a + b = x by a - b, the equation becomes a^2 - b^2 = x * (a - b).

### What is the result of simplifying a^2 and b^2?

-a^2 simplifies to x - 1/x and b^2 simplifies to 1 - 1/x, making a^2 - b^2 = x - 1.

### How do you simplify the equation further after finding a^2 - b^2?

-Dividing both sides of the equation by x, we get (x - 1)/x = a - b.

### What equation do you get after adding the two simplified equations together?

-After adding, the b terms cancel out, resulting in 2a = x + 1 - 1/x.

### How is the quadratic equation formed and solved?

-By recognizing that x - 1/x is a^2, we substitute into 2a = a^2 + 1, leading to the quadratic equation a^2 - 2a + 1 = 0, which gives a double root of a = 1.

### What is the final equation for x after solving for a?

-We substitute a = (x - 1/x)^(1/2) = 1, square both sides, and multiply by x, resulting in the quadratic equation x^2 - x - 1 = 0.

### What are the roots of the quadratic equation?

-The two roots are the golden ratio (1 + sqrt(5))/2 and its negative reciprocal (1 - sqrt(5))/2.

### Why is the negative root not a valid solution?

-The sum of two square roots must be non-negative, but the negative root leads to a negative x, which contradicts this requirement.

### What is the final solution to the problem?

-The solution is the golden ratio, (1 + sqrt(5))/2, which satisfies the original equation.

### Outlines

### 🔢 Introduction to the Problem

In this segment, Presh Talwalkar introduces the problem where the goal is to solve for the real values of x in the given equation. The equation involves two terms raised to the power of one-half. He thanks a viewer for suggesting the problem and encourages viewers to pause the video to attempt solving it before proceeding.

### 🧠 Strategy for Solving the Problem

Presh begins solving the problem using substitutions. He defines two new variables, a and b, representing the two terms in the original equation. The equation is then transformed into a simpler form: a + b = x. The plan is to multiply both sides of the equation by a - b, resulting in a difference of squares for further simplification.

### ✏️ Simplifying the Equation

The simplification process continues by applying the difference of squares formula. Presh expresses a² and b² in terms of x, which leads to a new equation where a² - b² is equal to x - 1. The equation is then divided by x, and the expression is flipped for convenience. This allows the equation to become simpler and more manageable.

### ➕ Adding and Simplifying

The process moves forward as the two equations are added together, which causes the b terms to cancel out. The result is 2a = x + 1 - 1/x. Presh simplifies the right-hand side and substitutes x - 1/x back as a², yielding a quadratic equation in terms of a.

### 🧮 Solving the Quadratic Equation

Presh solves the quadratic equation by factoring and obtaining a double root, where a is equal to 1. With a solved, he recalls that a represents the expression (x - 1/x) raised to the power of one-half. He squares both sides and multiplies through to arrive at a standard quadratic equation: x² - 1 = x.

### ✨ The Golden Ratio Solution

The quadratic equation yields two roots: one is the golden ratio (1 + √5)/2, and the other is its negative reciprocal (1 - √5)/2. Presh tests these roots in the original equation and finds that the negative root is not valid, as it results in a contradiction. The golden ratio is confirmed as the correct solution.

### 🎉 Conclusion and Reflection

Presh concludes by emphasizing that the golden ratio is the solution to the equation and describes it as a 'divine answer.' He thanks the community for their support and wraps up the episode, inviting viewers to return for more problem-solving videos.

### Mindmap

### Keywords

### 💡Substitution

### 💡Difference of squares

### 💡Quadratic equation

### 💡Golden ratio

### 💡Reciprocal

### 💡Simplification

### 💡Square root

### 💡Factoring

### 💡Negative solution

### 💡Real values

### Highlights

Solve for real values of x in a tricky equation involving square roots.

The equation is simplified using substitutions for clever problem-solving.

The original equation is transformed into a sum of terms involving square roots.

By multiplying both sides by the difference of terms, the equation becomes a difference of squares.

Substitution leads to the expression x - 1 being equal to another simplified form.

The right-hand side is further simplified, revealing a key relationship between terms.

After some algebraic manipulation, the problem reduces to a solvable quadratic equation.

Solving the quadratic equation yields two possible roots.

The golden ratio appears as one of the solutions to this mathematical problem.

We dismiss the negative root as it leads to an impossible solution.

Verification shows that the golden ratio is the correct solution to the original equation.

The golden ratio provides a 'divine' answer to the tricky equation.

This example showcases a blend of algebraic techniques and the elegance of mathematical solutions.

The problem-solving strategy involves both intuitive and formal methods of simplification.

The episode highlights a mathematical approach that combines creativity with rigor.

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