Question

Factor completely x³ - 7x² + 2x + 40 given x = -2 is a root.

Answer 1

Answer:

  (x +2)(x -4)(x -5)

Step-by-step explanation:

When you divide the cubic by (x +2), the factor that has -2 as a root, you get a quadratic with roots 4 and 5. Thus the factors are ...

  (x +2)(x -4)(x -5)

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In the attachment, we have done the division using a graphing calculator. You can also do it by polynomial long division or by synthetic division. The resulting quadratic is ...

  x^2 -9x +20 = (x -4)(x -5) . . . . . factor the quadratic