(x-1)(x-3)(x+5)(x+7)-297=0

4 min read Jun 17, 2024
(x-1)(x-3)(x+5)(x+7)-297=0

Solving the Quartic Equation: (x-1)(x-3)(x+5)(x+7) - 297 = 0

This article explores the process of solving the quartic equation (x-1)(x-3)(x+5)(x+7) - 297 = 0.

Expanding and Simplifying

The first step involves expanding the equation by multiplying the factors:

  • (x-1)(x-3) = x² - 4x + 3
  • (x+5)(x+7) = x² + 12x + 35

Now, we need to multiply these two quadratic expressions:

  • (x² - 4x + 3)(x² + 12x + 35) = x⁴ + 8x³ - 29x² - 126x + 105

Finally, we can subtract 297 from both sides to get the simplified quartic equation:

  • x⁴ + 8x³ - 29x² - 126x - 192 = 0

Factoring the Equation

Our aim is to factor the quartic equation into simpler factors. This is where a little observation and manipulation are key:

  1. Grouping Terms: Rearrange the terms to facilitate factoring:
    • (x⁴ - 192) + (8x³ - 29x²) - 126x = 0
  2. Difference of Squares: Recognize the first term as a difference of squares:
    • (x² - √192)(x² + √192) + x²(8x - 29) - 126x = 0
  3. Factor out Common Factors: Factor out common factors in the second and third terms:
    • (x² - √192)(x² + √192) + x²(8x - 29) - 63(2x) = 0
  4. Further Grouping: Group the terms to find a common factor:
    • (x² - √192)(x² + √192) + (x² - 63)(8x - 29) = 0

Now, we have factored the equation into two parts, each of which can be further simplified:

  • (x² - √192)(x² + √192) = (x - √√192)(x + √√192)(x - i√√192)(x + i√√192)
  • (x² - 63)(8x - 29) = (x - √63)(x + √63)(8x - 29)

Final Solution

By combining the factors, we arrive at the complete factored form of the equation:

  • (x - √√192)(x + √√192)(x - i√√192)(x + i√√192)(x - √63)(x + √63)(8x - 29) = 0

Therefore, the solutions to the equation are:

  • x = √√192
  • x = -√√192
  • x = i√√192
  • x = -i√√192
  • x = √63
  • x = -√63
  • x = 29/8

These are the seven distinct roots of the quartic equation.

Conclusion

Solving the equation (x-1)(x-3)(x+5)(x+7) - 297 = 0 involved a series of steps: expanding, simplifying, factoring, and isolating the roots. The solution reveals seven distinct roots, including real and complex solutions. This process illustrates the powerful tools of algebra and factorization in solving polynomial equations.

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