Michelle V.

asked • 01/14/20

Function zero problem

find all rational zeros of this function


f(x) = 3x4 + 16x3 - 59x2 - 400x - 400

1 Expert Answer

By:

Doug C.

Nice presentation. Just commenting because I was working on this when I noticed your answer. That last quadratic does in fact factor. the two additional rational roots are -5 and -4/3.
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01/14/20

William P.

tutor
Thanks Doug, and thank you for the correction.
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01/14/20

William P.

tutor
Hello Michelle, Thanks to Doug C., I realize I made a mistake on the last part of the problem. The "reduced equation" 3x^2 + 19x +20 = 0 does indeed have rational solutions. You can solve the equation by factoring as follows: 3x^2 + 19x +20 = 0, which becomes (3x + 4)(x + 5) = 0, and so x = -4/3 and x = -5. So there are four rational zeros, 5,-4, -4/3, and -5. Sorry for the confusion! William
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01/14/20

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