(x-1/x+1)^4-13(x-1/x+1)^2+36=0

3 min read Jun 17, 2024
(x-1/x+1)^4-13(x-1/x+1)^2+36=0

Solving the Equation: (x-1/x+1)^4 - 13(x-1/x+1)^2 + 36 = 0

This equation might seem intimidating at first, but we can solve it using a clever substitution. Let's break down the process:

1. Substitution

Let y = (x-1/x+1). Substituting this into our equation gives us:

y⁴ - 13y² + 36 = 0

2. Factoring the Quadratic

Now we have a quadratic equation in terms of y². This equation can be factored:

(y² - 9)(y² - 4) = 0

This gives us two possible solutions:

  • y² - 9 = 0
  • y² - 4 = 0

3. Solving for y

Solving these equations for y, we get:

  • y² = 9 => y = ±3
  • y² = 4 => y = ±2

4. Back Substitution

Now we need to substitute back our original expression for y:

  • Case 1: y = 3 (x-1/x+1) = 3
  • Case 2: y = -3 (x-1/x+1) = -3
  • Case 3: y = 2 (x-1/x+1) = 2
  • Case 4: y = -2 (x-1/x+1) = -2

5. Solving for x

Now, we need to solve each of these equations for x:

Case 1: (x-1/x+1) = 3

  • Multiply both sides by (x+1): x-1 = 3(x+1)
  • Expand and solve for x: x-1 = 3x + 3 => -4 = 2x => x = -2

Case 2: (x-1/x+1) = -3

  • Follow similar steps as Case 1 to get x = 1/2

Case 3: (x-1/x+1) = 2

  • Follow similar steps as Case 1 to get x = -3

Case 4: (x-1/x+1) = -2

  • Follow similar steps as Case 1 to get x = 1

6. Solution

Therefore, the solutions to the equation (x-1/x+1)⁴ - 13(x-1/x+1)² + 36 = 0 are:

x = -2, x = 1/2, x = -3, and x = 1

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