Chapter 6: Problem 25
What is the value of \(\sqrt{6}+\sqrt{6+\sqrt{6+\cdots}}\) ?
Short Answer
Expert verified
The value is \(3 + \sqrt{6}\).
Step by step solution
01
Define the Infinite Expression
Let's define the expression \( x \) such that \( x = \sqrt{6 + \sqrt{6 + \sqrt{6 + \cdots}}} \). This means \( x = \sqrt{6 + x} \) since the expression inside is identical to the whole expression.
02
Square Both Sides
To eliminate the square root, square both sides of the equation: \( x^2 = 6 + x \).
03
Rearrange the Equation
Move all terms to one side to form a standard quadratic equation: \( x^2 - x - 6 = 0 \).
04
Solve the Quadratic Equation
Factor the quadratic equation: \( (x - 3)(x + 2) = 0 \). This gives the solutions \( x = 3 \) and \( x = -2 \).
05
Choose the Valid Solution
Since \( x \) represents a length (as it is derived from square roots), it must be non-negative. Therefore, \( x = -2 \) is not a valid solution. We have \( x = 3 \).
06
Calculate the Final Expression
Add \( \sqrt{6} \) to the solution of the infinite expression: \( \sqrt{6} + 3 = 3 + \sqrt{6} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Equation
Quadratic equations play a vital role in algebra, especially when dealing with infinite radicals or nested expressions. A quadratic equation is any equation that can be rearranged to the standard form: \[ ax^2 + bx + c = 0, \] where \(a\), \(b\), and \(c\) are constants, and \(x\) represents an unknown variable. In our exercise, after defining the infinite radical expression, we arrived at the equation:
- \(x^2 = 6 + x\)
- \(x^2 - x - 6 = 0\)
- \(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\).
Algebraic Manipulation
Algebraic manipulation involves rearranging equations to make them simpler or to solve for a variable. With infinite radicals, this often means transforming a complex expression into a more manageable form. In our specific problem, it was necessary to define the infinite radical as \(x\):
- \(x = \sqrt{6 + x}\)
- \(x^2 = 6 + x\)
Mathematical Inductive Reasoning
Mathematical inductive reasoning is a method of solving problems and providing proof by observing patterns and testing assumptions. In the context of infinite radicals, it is crucial in arriving at a self-identifying expression, \(x\), such as:
- \(x = \sqrt{6 + x}\)