(2x-7)(x^2-9)(2x+5)=91

3 min read Jun 16, 2024
(2x-7)(x^2-9)(2x+5)=91

Solving the Equation: (2x-7)(x^2-9)(2x+5)=91

This problem involves solving a polynomial equation. Let's break down the steps to find the solutions for x:

1. Expand the Equation

First, we need to expand the equation by multiplying the factors:

  • Expand (x^2-9): This is a difference of squares, which simplifies to (x+3)(x-3).
  • Multiply the three factors: (2x-7)(x+3)(x-3)(2x+5) = 91

2. Simplify the Equation

  • Multiply the first two factors: (2x^2 - x - 21)(x-3)(2x+5) = 91
  • Multiply the result by (x-3): (2x^3 - 7x^2 - 34x + 63)(2x+5) = 91
  • Finally, multiply by (2x+5): 4x^4 - 4x^3 - 113x^2 + 101x + 315 = 91

Now we have a fourth-degree polynomial equation: 4x^4 - 4x^3 - 113x^2 + 101x + 224 = 0

3. Finding Solutions

Unfortunately, there's no simple formula to directly solve fourth-degree equations. Here are common methods:

  • Factoring: Try factoring the polynomial. It might be possible to factor it into smaller expressions, leading to solutions. However, this might be complex for a fourth-degree polynomial.
  • Rational Root Theorem: This theorem helps identify potential rational roots of the polynomial. You can test these roots using synthetic division or by plugging them into the equation.
  • Numerical Methods: For complex polynomials, numerical methods like the Newton-Raphson method or graphing calculators can provide approximate solutions.

4. Conclusion

Solving the equation (2x-7)(x^2-9)(2x+5)=91 involves expanding, simplifying, and then using appropriate methods to find the solutions for x. The exact solutions might require numerical methods or might involve complex numbers.

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