SOLUTION: Find a cubic equation in standard form with intergral coefficient that has 4 and 2-i as roots

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Question 1133828: Find a cubic equation in standard form with intergral coefficient that has 4 and 2-i as roots
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
roots are 4, 2-i and 2+i
factors are (x-4)(x-2+i)(x-2-i)
the latter two factors multiply to
x^2-2x-ix-2x+4+2i+ix-2i+1 (-i^2)
this is x^2-4x+5
multiplying that by x-4 yields
x^3-4x^2-4x^2+16x+5x-20
x^3-8x^2+21x-20
graph%28300%2C300%2C-5%2C5%2C-100%2C100%2Cx%5E3-8x%5E2%2B21x-20%29