algebra

use variable substitution and factoring to find all of the roots of each equation.

x^4-9x^2+18=0

how do you do this??

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asked by Lauren
  1. you need, of course, to factor this.
    Start by doing this:

    (x^2 - )(x^2 - ) =0

    Can you fill in the blanks?

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    posted by DanH
  2. is it (x^2 - 6) (x^2 - 3) ??

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    posted by Lauren
  3. yes!! so you have it factored. Then to get the "roots," set each one equal to 0.

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    posted by DanH
  4. so then its x^2-6 =0 and ^2-3=0 and the don't i put the root sign over the x^2 to get rid of the x^2? and then i end up with x + or - the suare root of 6 = 0 or is that wrong??

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    posted by Lauren
  5. yes....
    you have x^2 - 6 = 0,
    so, x = + and - sqrt6

    AND

    x^2 - 3 = 0,
    so, x also = + and - sqrt3

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    posted by DanH
  6. so is that it?? simple as that?

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    posted by Lauren
  7. yup, simple as that!!

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    posted by DanH
  8. but then the directions say variable substitution

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    posted by Lauren
  9. I'm sorry. I really don't know what they mean by "variable substitution!"

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    posted by DanH
  10. alright thanks anyway

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    posted by Lauren
  11. x^2-x-?=(x+2)(x-?)

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    posted by bre

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