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March 27, 2015

March 27, 2015

Posted by **jay** on Friday, October 14, 2011 at 3:30am.

- algebra 2 -
**Jai**, Friday, October 14, 2011 at 7:28am*i think you mean the ZEROS / ROOTS are 5, 2i and -2i.

if so, you can get them by multiplying and expanding,

(x-5)(x-2i)(x+2i)

note that 1 = sqrt(-1)

but an easier method would be, to start with the roots 2i and -2i. recall that q quadratic equation follows the formula,

x^2 - (sum of roots)*x + (product of roots)

thus, substituting 2i and -2i:

x^2 - (2i - 2i)*x + (2i)*(-2i)

x^2 - (0)*x - 4*(i^2)

x^2 - 4*(-1)

x^2 + 4

now, we multiply this by (x-5):

(x-5)(x^2 + 4)

x^3 - 5x^2 + 4x - 20

hope this helps~ :)

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