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Factor x^4 - 2x^3 - 33x^2 + 50x + 200 completely using the given factor x^2 - 25.

1 Answer

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You can do synthetic division twice immediately (or once if you know how to handle x^2 - 25 all at once. I'll use 2 divisions. x^2 - 25 is (x + 5)(x - 5). Both of them are zeros to the given equation which means that x = +5 and

x = - 5 are both zeros of the given quartic.

5 1 -2 -33 50 200

5 15 -90 -200

=====================================

1 3 -18 -40 0

What you have now is x^3 + 3x^2 - 18x - 40 = 0

Do another synthetic division

-5 1 3 -18 -40

-5 10 40

============================

1 -2 -8 0

The result is

x^2 - 2x - 8 = 0 which factors.

(x + 2)(x - 4) = 0

Answer

The factors are (x + 2)(x - 4)(x + 5)(x - 5) = 0

Long division

x^2 + 0 + 25 ||x^4 - 2x^3 - 33x^2 + 50x + 200 ||x^2 - 2x - 8

x^4 + 0 + 25x^2

==================

-2x^3 -8x^2 + 50x

-2x^3 + 0 + 50x

=================

-8x^2 + 0 +200

-8x^2 + 0 + 200

==================

0

User Skitzafreak
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