SOLUTION: find th values for which the rational expression is undefined -6+9x/x^3-8x^2+7

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Question 774384: find th values for which the rational expression is undefined -6+9x/x^3-8x^2+7
Answer by lwsshak3(11628) About Me  (Show Source):
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find the values for which the rational expression is undefined -6+9x/x^3-8x^2+7
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expression is undefined if denominator=0
x^3-8x^2+7=0
solve for x using rational roots theorem:
....0...|.....1.......-8........0.........7.....
....1...|.....1.......-7......-7.......-7 (1 is a root)
(x-1)(x^2-7x-7)
x^2-7x-7=0
solve by quadratic formula:
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a=1, b=-7, c=-7
x≈0.8875
or
x=7.8875
expression is undefined if: x=1, 0.8875, or 7.885