math

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Use factoring by grouping to solve the following equation.
4x3 + 8x2 − 9x − 18 = 0
x = 1 (smallest value)
x = 2
x = 3 (largest value)

  • math -

    x = 1 is not a solution. You can easily prove that yourself.

    When x = 2,
    4x^3 + 8x^2 − 9x − 18 = 28

    So that is not a solution, either. Neither is x = 3. How did you come up with your answers?

    When x = -2,
    -32 +32 +18 -18 = 0

    So x+2 is a factor of the polynomial.
    The other factor is
    (4x^3 + 8x^2 − 9x − 18)/(x+2)
    = (4x^2 -9) = (2x +3)(2x-3)

    So the other two solutions are
    x = 3/2 and x = -3/2

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