Question

Find the zeros of x^3 + 2x^2 - 9x - 18


show all of your work

Answer 1

• {-3; -2, 3}

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Factorize the polynomial in below steps:

• x³+ 2x² - 9x - 18 =
• x²(x + 2) - 9(x + 2) =
• (x + 2)(x² - 9) =
• (x + 2)(x + 3)(x - 3)

Make each factor equal to zero:

• x + 2 = 0 ⇒ x = - 2
• x + 3 = 0 ⇒ x = - 3
• x - 3 = 0 ⇒ x = 3

Hence the zeros are -3, -2 and 3.